AURT366108A LWB Word - Learning Research & …lrd.kangan.edu.au/.../AURT366108A/AURT366108A_LWB_PDF.pdfBatteries Batteries contain sulphuric acid (H2SO4). Battery acid will destroy

AUR30405 CERTIFICATE III IN AUTOMOTIVE MECHANICAL TECHNOLOGY

AURT366108A Carry out diagnostic procedures

LEARNER WORKBOOK

© Commonwealth of Australia 2011

ISBN: 978‐1‐876838‐25‐6

This document is available under a “Free for Education” licence for educational purposes – see http://www.aesharenet.com.au/FfE2 for details.

This work is copyright. You may download, display, print and reproduce this material in whole or in part or in modified form (retaining this notice) for your personal, non‐commercial use or use within your organisation. If you use, display, or reproduce this material or a modified form of it in whole or in part within your organisation you must include the following words in a prominent location within the material in font not less than size 12: ‘The views expressed in this publication do not necessarily represent the view of the Minister for Education or the Australian Government. The Australian Government does not give any warranty nor accept any liability in relation to the contents of this work’. Apart from any use as permitted under the Copyright Act 1968, all other rights are reserved. Requests and inquiries concerning reproduction and rights should be addressed to the Commonwealth Copyright Administration, Attorney General’s Department, Robert Garran Offices, National Circuit, Barton ACT 2600 or posted at http://www.ag.gov.au/cca.

Funded under the Workplace English Language and Literacy (WELL) Program by the Australian Government Department of Education, Employment and Workplace Relations.

The views expressed in this publication do not necessarily represent the view of the Minister for Education or the Australian Government. The Australian Government does not give any warranty nor accept any liability in relation to the contents of this work.

AURT366108A Carry out diagnostic procedures 1

Elements: ......................................................................................................... 1 About the workbook ..................................................................................... 1 Assessment ...................................................................................................... 3 Skills Recognition ............................................................................................ 4 Access and equity ......................................................................................... 4

Introduction 5

What is ‘diagnosis’? ....................................................................................... 5 What is ‘normal’ and ‘abnormal’? ............................................................. 6 What is a diagnostic procedure? ................................................................ 6 Safety ............................................................................................................... 7 Tasks and hazards .......................................................................................... 8 Activity 1 ........................................................................................................ 9

Carrying out automotive diagnosis 11

The importance of diagnosis ...................................................................... 11 Symptoms, faults and causes .................................................................... 13 Activity 2 ...................................................................................................... 17 The steps in a diagnostic procedure ........................................................ 22 Gathering information for diagnosis ......................................................... 23 Types of diagnostic procedures ................................................................ 24 Activity 3 ...................................................................................................... 27

Six-step diagnostic procedure 29

Apply six-step diagnosis to a real problem .............................................. 32 Activity 4 ...................................................................................................... 37 Activity 5 ...................................................................................................... 41

Reporting and documenting diagnosis and repairs 43

Why do we need to document the diagnostic process? ..................... 43 Activity 6 ...................................................................................................... 49 Writing a diagnostic report ......................................................................... 53 Parts of a Report .......................................................................................... 54 Activity 7 ...................................................................................................... 57

Other diagnostic approaches 59

Branching diagnostic procedures............................................................. 59 Activity 8 ...................................................................................................... 61 ‘Black Box’ Diagnosis ................................................................................... 63

On-Board Diagnostics ................................................................................. 65 Reading codes and information with a scan tool .................................. 68 Proprietary and generic scan tools ........................................................... 69 What information is available from an OBD system? ............................. 70 Activity 9 ...................................................................................................... 75 Activity 10 .................................................................................................... 79

Glossary 81


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AURT366108A Carry out diagnostic procedures This unit covers the competence required to diagnose component/equipment faults from different symptoms and to nominate repair action.

Elements: 1. Prepare to diagnose faults

2. Apply technology to isolate fault(s)

3. Recommend rectification method(s)

4. Component/equipment is prepared for customer use

About the workbook This workbook is designed to assist you in gaining underpinning knowledge and developing practical skills to achieve the competency standard AURT366108A Carry out diagnostic procedures within the context of light vehicles.

This workbook contains:

information

questions

practical activities

directions to use additional resources.

The workbook is divided into stages. At the end of a stage, you will see an icon (picture with a meaning) asking you to check your answers and/or practical activities with your trainer. This helps the trainer to monitor your progress.


2

What do the icons mean? An icon is a picture with a meaning. In the workbook, these icons tell you something about:

what to do next (activity, check your answers, watch a video clip) or

the text (this is a safety warning).

Complete an activity

Check your answers with your trainer

Watch this video clip

Safety warning


3 3

Assessment To meet the assessment requirements for this competency standard you must demonstrate the following:

Knowledge of:

OH&S regulations/requirements, equipment, material and personal safety requirements

diagnostic procedures and problem‐solving techniques

symptom and cause differentiation

work organisation and planning processes

enterprise quality procedures

document responsibilities

document procedures.

Practical ability to:

Develop a diagnosis strategy to determine a fault

Carry out systematic diagnosis to test for a range of faults, using meters/ gauges/ measuring equipment

Interpret test results and identify the actual fault/s

Recommend rectification method/s.

Report findings in approved workplace format


4

Skills Recognition You may already have knowledge and skills for all (or part) of this competency standard. If you believe you can demonstrate that you already have the skills and knowledge required, talk to your trainer about applying for Skills Recognition.

This is also known as Recognition of Prior Learning (RPL), Recognition of Current competence (RCC), or simply Recognition.

Skills Recognition is a process for gaining credit for those skills and knowledge gained through work experience, formal training or other life experience.

Access and equity In training, access and equity means ensuring that people with differing needs and abilities have the same opportunities to successfully gain skills, knowledge and experience through education and training. It is about removing barriers and providing the supports people need to access, participate and achieve, irrespective of their age, disability, colour, race, gender, religion, sexuality, family responsibilities or location.

For students with disabilities, training organisations may make adjustments to ensure equal opportunity. Reasonable adjustments are designed to minimise the disadvantage experienced by learners with a disability and can include administrative, physical or procedural modifications.

NOTE: If you believe you could benefit from support to help you overcome a barrier to participation, you should speak to your trainer or the person in your RTO responsible for access and equity.


5 5

Introduction This workbook assumes that you have already achieved competence in all the other vehicle systems you need for your work.

The workbook will help you to develop skills in applying your technical knowledge in a systematic way to diagnose faults in vehicles or other machinery.

The workbook uses the term ‘vehicle’ but all the processes and procedures can also be applied to other machines or pieces of equipment.

What is ‘diagnosis’? Motor vehicles (or machines or other equipment) sometimes break down. They develop faults or problems, and repair technicians (that’s you) need the knowledge and skills to:

find the cause of the fault, and

fix it.

The first step is called ‘fault diagnosis’.

How do you do it? Guessing is not good enough ‐ you need to make a systematic, logical series of checks to identify the fault. You need:

a sound knowledge of the principles and operation of the system or component being checked

to be able to recognise whether a component is working normally or not

to think carefully about all the things that could cause a particular fault

to test each possible cause to identify (or diagnose) the actual problem.

Diagnosis is the process of identifying a fault, determining its cause and selecting possible solutions. Sometimes it is called ‘trouble shooting’ or ‘fault finding’.


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What is ‘normal’ and ‘abnormal’? Everything in a vehicle is in either a ‘normal state’ or an ‘abnormal state’.

Normal means things are okay; they are the way they should be.

Abnormal means things are NOT okay, or NOT the way they should be.

We can say that either ... the steering is working normally, or it is not.

... the alternator is charging normally, or it is not.

... the handbrake is working normally, or it is not.

We can also talk about ‘normal events’ and ‘abnormal events’. An event is something that happens. An event occurs when a gear is selected, or a turn signal lights up, or the cooling fan turns on.

A normal event is when something happens in exactly the way it should.

An abnormal event is when something happens NOT in the way it should.

For example, the engine misses, the steering loses power assistance, or a rod comes out through the side of the engine block.

The purpose of all motor vehicle diagnosis is:

to recognise abnormal states and abnormal events

to find the cause of those abnormal things, and

to recommend repairs which will return the vehicle to its normal state of operation.

What is a diagnostic procedure? A procedure is a logical set of steps to follow. Using a logical procedure will help you to diagnose a vehicle’s problem quickly and efficiently. All diagnostic techniques are based on logical thinking and a systematic approach to solving the problem. They often take the form of a diagram or flow chart.

You might find diagnostic procedures in the vehicle manufacturer’s workshop manual, or you might make one up yourself based on your knowledge and experience.

This workbook explains how to use and develop diagnostic procedures.


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Safety All diagnostic procedures must be carried out safely. Working safely helps prevent injury to yourself and others. It also prevents damage to the vehicle or test equipment.

Today’s sophisticated vehicle systems (such as electronic systems for engine, transmission and body management; anti‐lock brakes and vehicle stability control) can easily be damaged by unsafe or careless test and repair procedures.

Any damage or injury in the workplace can be very costly – look at some of the costs in the table below.

Damage or injury Costs

Injury to a worker pain, possible disablement

medical costs

loss of income

government safety inspections

increased workplace insurance premiums

Damage to a vehicle cost to the workshop

reduced profits

damaged reputation

Make sure you follow all:

Occupational Health and Safety (OHS) guidelines

safety instructions from your employer

vehicle or system safety precautions given by the vehicle manufacturer.

ALWAYS wear suitable Personal Protective Equipment (PPE). Minimum PPE requirements are:

glasses or mask to protect eyes from flying particles and liquid sprays

gloves for handling hot items and chemicals

suitable neat‐fitting overalls or clothing

safety footwear.

Some jobs will require specialised equipment, such as a respirator. Any supplied PPE must be used when a job requires it.

THINK SAFETY at all times


8

Tasks and hazards Here are some of the risks and hazards you may be exposed to when doing diagnosis and repair tasks:

Hazard Advice

Fire Watch out for fuel leaks when working on fuel systems. Eliminate anything which could start a fire.

Keep a fire extinguisher nearby.

Lifting Never lift more than you can manage.

Ask for help, or use lifting equipment.

Exhaust Gases Running engines need good ventilation.

Carbon monoxide (CO) in the exhaust can kill you.

Other exhaust chemicals can cause asthma and cancer.

Running Engines

Don’t wear loose clothing when working around a running engine.You could be dragged into drive belts or other moving parts.

Electric Shock Ignition systems produce voltages of 30,000 to 50,000 volts.

Reaction to an accidental shock can throw you into contact with moving parts such as the fan or drive belts.

Batteries Batteries contain sulphuric acid (H2SO4).

Battery acid will destroy clothing, burn skin, and can cause blindness if it gets in your eyes.

Batteries also generate explosive hydrogen gas (H2) when charging, so keep sparks away.

Figure 1: Be careful with battery acid


9 9

Activity 1

Tick the correct answer/s. There may be more than one correct answer.

Question 1 The term ‘diagnosis’ means:

Using a scan tool to extract codes

Using a logical process to solve problems

Repairing faulty components

Replacing faulty components.

Question 2 When a vehicle component or system is working the way it should be, we say that it is in:

A normal state

An abnormal state

A paranormal state

A sub‐normal state.

Question 3 An automatic transmission, on up‐shift, always makes a 2nd to 4th change and never selects 3rd. Is this:

A normal event?

An abnormal event?

A paranormal event?

A sub‐normal event?


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Question 4 Personal Protective Equipment (PPE) for technicians working in an automotive workshop should include:

Eye protection‐ glasses or face mask

Gloves to protect hands from burns and chemicals

Skin protection‐ overalls or suitable protective clothing

Over‐lapping steel abdominal protection when balancing wheels

Safety footwear.

Question 5 Working around any of the vehicle systems listed below can be dangerous. Describe (write down) some possible dangers associated with each system:

Fuel system ______________________________________________________________________

_________________________________________________________________________________

Ignition system ___________________________________________________________________

_________________________________________________________________________________

Batteries ________________________________________________________________________

_________________________________________________________________________________

Running engines __________________________________________________________________

_________________________________________________________________________________

Ask your trainer to check your results before proceeding.

Trainer Signature: .............................................................. Date: .....................


11 1

1

Carrying out automotive diagnosis The importance of diagnosis Diagnosis is an extremely important task in today’s workshop. Fast, accurate diagnosis can save money for both the customer and the workshop.

The table below shows some of the benefits of good diagnosis for the three stakeholders in automotive repair.

Who? Benefits

The customer Time and money has not been wasted on inefficient diagnosis methods

Their vehicle is off the road for the minimum amount of time

No re‐work required through wrong diagnosis

The technician Skilled and efficient employees are valued and rewarded by their employer

They have the satisfaction of doing a good job

The workshop The job is completed in the shortest possible time, and productivity (time spent per job) is improved so more jobs can be completed in a day

Warranty costs are down because the work is high‐quality

Bad or careless diagnosis can have just the opposite effect.

Figure 2: The result of bad diagnosis

Not systematic. Takes longer to carry out & costs more

Might be the wrong diagnosis and the wrong repair

Results in a ‘re‐work’ Costs the workshop even more in wasted time

A very unhappy customer! Decides to take her/his vehicle somewhere else in the future

© Commonwealth of Australia 2011 12

Which technician would you choose?

Technician 1 ‐ Guessing Technician 2 ‐ Logical diagnostic procedure

Joe Goodenough took the van for a quick test run.

Joe didn’t do any more checks.

Jack Getitryte carried out a few more tests and collected more information, including looking in the workshop manual.

Jack checked and found that the rear axle shims or wedges (which set the drive line angle) were missing, left out after a previous repair.

A rebuilt transmission was fitted and road tested.

The noise was exactly the same as before!

The shims were replaced and the problem was cured!

I bought this van second hand not long

ago– it’s a rear wheel drive. When I

accelerate, there’s a loud grinding and

groaning noise, and also a bit of vibration.

What could it be?

The noise seems to be coming from the manual transmission. It’s an old vehicle, so the transmission bearings are probably faulty.

I think the transmission needs rebuilding.

The manual says that one reason for noise and vibration on acceleration can be incorrect driveline angles. I’ll check to see if that could be the problem.


13

Symptoms, faults and causes Understanding the language When we diagnose a problem, we look at the symptoms of the fault and try to find the cause of them. What do these words mean?

Symptom

A symptom is a clue that something is wrong. It is a noticeable change ‐ we might see, hear, smell or feel something different.

These are both symptoms of a problem. The owner or driver recognises them as abnormal. They won’t know what the fault is, but will know that something about the car is different.

A problem or fault in a vehicle is usually first noticed by the regular driver of the vehicle, because they are most familiar with the way it normally operates, and spend a lot of time behind the wheel.

It is the technician’s job to look at the symptom and work out what fault has caused it.

These symptoms are the abnormal things that the driver has noticed about the performance of her/his vehicle. They all point to some problem which has produced the symptom.

The engine cuts out!

The clutch feels funny...

In fifth gear, the engine revs hard but the car won’t accelerate normally. The front tyres

have worn out very quickly.

The engine stopped suddenly, and it won’t re‐start.


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Fault

A fault is an abnormal condition in a system or component. Something has gone wrong which we need to identify and repair.

Faults may be:

Hardware faults ‐ Physical faults that we can observe or measure, such as parts which are

broken, worn, out‐of‐specification, damaged, incorrectly adjusted or assembled.

Software faults ‐ May not be directly observable, such as faulty, incorrect or corrupted

programs in electronic modules.

The fault may be one or more of the following things:

Type of fault Example

Not working at all A blown headlight globe

A failed open circuit fuel injector

Working, but not the way it was designed to work

Working headlights which are badly aimed

A fuel injector with a faulty spray pattern

Doing something it is not supposed to do

A headlight that won’t turn off

A fuel injector with a constant leak

Making something undesirable happen

Causing the headlight fuse to blow

Generating excessive exhaust emissions.

Here are some examples of symptoms reported and the faults which were found to match them:

Symptom Fault

In fifth gear, engine revs hard but car won’t accelerate

Slipping clutch

Excessive tyre wear Incorrect wheel alignment

Engine stopped suddenly, won’t re‐start Broken cam belt, bent valves

These faults can be repaired by replacement of parts, or by adjustment.

But what caused those faults?

There are many reasons why a clutch might slip, but if we simply fit a new clutch kit without discovering the underlying cause of the slippage, that vehicle might return to the workshop on the back of a tow‐truck!


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Cause

A symptom might indicate a fault in a customer’s vehicle, and a faulty (worn, broken) component might be found, but what produced that fault? Something must have caused that change.

Finding the cause of the faults will allow the technician to choose the right repair to correct the fault, and prevent any re‐work under warranty (‘come backs’).

Example:

Figure 3: the importance of finding the cause

Remember those symptoms and faults shown in the table above? Here are the some possible causes of those faults:

Symptom Fault Cause

In fifth gear, engine revs hard but car won’t accelerate

Slipping clutch Clutch driven plate worn out after 200,000km of service. Normal wear.

Excessive tyre wear Incorrect wheel alignment

Bent steering arm ‐ impact with road gutter

Engine stopped suddenly, won’t re‐start

Broken cam belt, bent valves

Belt overdue for replacement. Leaking camshaft oil seal.

Symptom Instrument panel oil light is on when the engine is running

Fault Engine oil level is low

Cause Technician didn’t find the cause of the low oil level

Action Technician tops up the oil, checks that the oil light is now off, and returns the car to the customer

Result That car will eventually come back with exactly the same symptom!


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Activity 2


Question 1 Accurate diagnosis is important because:

It can save the customer money

It can reduce workshop costs

It keeps customers happy with your work

It reduces the chance of having to do the job again.

Question 2 When diagnosis is quick, efficient and accurate:

Workshop productivity is improved

The technician’s skills are demonstrated and valued

The workshop can close early for the day

The customer gets his/her vehicle back in reasonable time at affordable cost.

Question 3 A symptom is:

A piece of equipment

Someone who has knowledge

A noticeable change

No change in operation.


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Question 4 Symptoms can be recognised because they:

Make vehicles perform normally

Change how something performs

Are imagined by the owner

Are a noticeable change in performance.

Question 5 A symptom is:

A sign that something is operating

An unnoticeable change in a vehicle’s operation

The failure of some component or system

A perceptible change in a vehicle’s operation.

Question 6 A fault is a component or system which is:

Not working at all

Not there at all

Not doing what it is supposed to be doing

Worn, broken or out of adjustment.

Question 7 A cause is:

When the vehicle fails completely

When only part of a system is working

The reason why a fault occurs

An abnormal state in a component or system.


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Question 10 Here are three statements about a vehicle with a problem.

Which is the symptom, fault, and cause?

Draw lines to match each statement with the correct box.

Question 11 Describe a simple problem that you have come across at work recently.

Write down the symptom, fault and cause of the problem. You may also explain your answer to your teacher.

SYMPTOM

FAULT

CAUSE



Sticking caliper slides on right front caliper

Noise and extreme heat coming from right wheel

Poor or lack of vehicle servicing

FAULT

CAUSE

SYMPTOM


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Diagnosing is not guessing Non‐technical people see a symptom and guess at the cause. But a technician doesn’t guess – they start to thing logically about what the cause of the fault could be.

If you want to find the cause which led to the fault and the symptom, you need to:

Gather more information about the complaint

Gather more information about the systems involved

Carry out a variety of tests

Think about (analyse) your information and test results; and

Confirm the cause of the problem.

Only then can you decide what repair is needed, and afterwards confirm that the fault and its cause have been eliminated.

One of my car’s parking lights isn’t working. The globe must be blown.

Well, the globe isn’t working, but I wonder why it’s not working? What has caused it?

I know that the globe is part of the lighting system, which is part of the electrical system. What are the most likely things which could cause this symptom of ‘light not working’?

Blown globe?

Blown fuse?

No supply voltage?

Not switched on?

Switching circuit fault?

Open circuit wiring harness?

Corroded connections?

Supply voltage too high ‐ blown globe?

Body Control Module fault?

Vibration ‐ blown globe?

and possibly more.


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The steps in a diagnostic procedure The diagnostic procedure you should use in the auto repair industry is similar to what a doctor does when you walk into the surgery with a minor illness.

Diagnostic step What the doctor does

Gather more information about the problem

Asks what your symptoms are (cough/cold/dizziness/pain in the leg/head ...)

Gather more information about the systems involved

Asks questions ‐how long have you had the cough/cold? What sort of cough is it? Can you show me? Where is the pain? How bad is it?

Checks your past medical history in her records.

Carry out a variety of tests using test equipment

Uses a stethoscope to listen to the cough, measures blood pressure or temperature, probes or manipulates the painful area, x‐ray etc

Might also consult some other source of medical information eg books, internet, colleagues

Think about (analyse) the information and test results and reach a diagnosis

Considers all the information gathered, including test results

Compares this with her expert medical knowledge of the human body

Works out the cause of your problem

Decide on the “repair” Prescribes the treatment for your condition eg medication/physiotherapy/brain transplant etc

Confirm the cause of the problem.

Asks you to come back for a check‐up to make sure the problem is fixed

Your doctor follows a logical diagnostic procedure. She is able to treat you successfully because:

She has a very good understanding of the system in which the problem exists.

She applies a logical, systematic procedure to working out what the cause of the problem was.

You need to be able to do exactly the same to successfully diagnose vehicle faults!


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Internet Information‐ Never believe information you find on the Internet unless you are absolutely certain that it comes from either an official factory site, or is otherwise totally reliable.

Never trust anything you read on sites such as the one‐make forums‐ they are usually full of misinformation and myths.

Gathering information for diagnosis Following a procedure (a set of steps) is nothing new to automotive repair technicians. When you change a wheel on a vehicle you follow a procedure to make sure it is changed safely and refitted securely.

This procedure might be developed by the vehicle manufacturer or you can create your own procedures to follow. Sometimes you might combine these for a particular job.

Your knowledge Your diagnostic ability depends on a good knowledge and understanding of the system in which the problem exists. But you can’t know everything! Most technicians become very familiar with particular systems (engine management, for example) on a limited range of vehicles.

When you find that you don’t know enough about a vehicle system, where can you look for help?

Use other sources of information Gathering information is part of the diagnosis process and is often easily available. Some of the reliable sources you could use are:

Other technicians in the workshop

Workshop manuals, and manufacturer’s technical hot‐lines

Service bulletins from the manufacturer

Service information from industry and commercial associations e.g. AACC, IAME, Autotech.

Keep up-to-date As a professional, you should take every opportunity to improve your knowledge. Don’t leave it until you’re in the middle of a diagnosis job!

Keep your knowledge up to date through:

Workplace training

TAFE courses

trade association courses

technical journals (publications)

workshop manuals.


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Types of diagnostic procedures There are lots of different procedures for diagnosis of vehicle faults, but they are all logical and systematic. This workbook will deal with:

Step‐by‐step procedures

Branching procedures

‘Black box’ procedures.

Often a diagnostic procedure can be shown on a diagram. In the medical example described earlier, the doctor followed this step‐by‐step process:

Figure 4: Step‐by‐step procedure

This could be used as a general procedure to follow on other diagnosis tasks. Often you can make a few small adjustments to suit the particular job.


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Feedback Loops Here is another, slightly different, diagnostic chart. It has a “feedback loop” which prompts you to re‐test or do further tests if you don’t find the fault on the first attempt.

Figure 5: Feedback loop

You can see that both of these diagnostic procedure flow charts are quite similar. You could apply these procedures to many straightforward diagnosis jobs.

An easy diagnosis

A customer traded in his old car on a new one. A month or two later he returned to the dealership complaining that recently, when he had to make an emergency stop, there was “a groaning noise and the brake pedal felt funny”.

When he demonstrated this to the technician it was clear that he had simply felt the normal operation of the anti‐lock braking system in his new car which he had never experienced before. He was very pleased to be told that there was no problem, and to be given instructions on the correct way to use ABS in an emergency.

However, most diagnosis isn’t that simple.

Step 2

Gather information

Step 3

Carry out tests

Step 1

Verify fault exists

Step 5

Identify and repair

the fault

Step 6

Check to make sure

Fault not found

Step 4

Consider the

information


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Activity 3


Question 1 Which of these things are essential steps in any diagnostic procedure?

Carrying out tests

Analysing information

Substituting parts

Gathering information.

Question 2 Write the 6 actions on the left into the boxes. Put them in the best order to show a simple diagnostic procedure.

Consider the information

Repair the fault

Carry out more tests if needed

Verify that the fault exists

Check the fault is fixed

Gather information

1.

2.

3.

4.

5.

6.


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Question 3 When diagnosing vehicle faults, it is important to keep up with the latest information. What are some ways you could increase your knowledge of the systems you work on? List them below.

_________________________________________________________________________________

_________________________________________________________________________________

_________________________________________________________________________________

_________________________________________________________________________________

_________________________________________________________________________________

_________________________________________________________________________________

_________________________________________________________________________________

_________________________________________________________________________________

_________________________________________________________________________________

Question 4 A ‘feedback loop’ in a diagnostic procedure can:

Cause an abnormal noise in the audio system

Take you out of the procedure and direct you to another job

Prompt you to re‐test, or make extra tests

Give advice on how to arrange the wiring loom.


Trainer Signature: .............................................................. Date: ....................

.


Six-step diagnostic procedure Let’s look at each of those six steps in more detail.

1. Confirm the symptom Make sure that the customer’s concern is valid (true).

Try to reproduce the symptoms described by the customer or have the customer demonstrate the symptom to you. If you do a road test‐ make sure it is done in a safe manner!

2. Gather information A. Question the customer closely about their concern. Once they leave the workshop you won’t have easy access to them.

“When did you first notice the problem? What conditions was the vehicle operating under at the time? High load? Light load? In traffic? Cruising on the freeway? How long since the engine was started? What repairs or service have been done recently?”

B. Try the “look and feel” test, if the problem allows it. Carefully inspect suspect areas, looking for obvious leaks, breaks, stains, noises, loose or damaged wiring etc.

C. Use other information sources:

Your workplace colleagues‐ have any of them come across these symptoms before?

On‐board diagnostic trouble codes (more about this later)

Service bulletins relevant to that vehicle to see if it is a known problem or subject to a recall

Workshop manuals have trouble‐shooting guides

Trade associations have technical information lines for advice and/or vehicle specifications eg the australian automobile chamber of commerce (aacc), or the institute of automotive mechanical engineers (iame)

Commercial data suppliers‐ companies who sell automotive technical and repair information in book or digital form.

SOME HINTS:

Gather as much information as possible at the beginning of the job.

Never overlook the obvious.

Look for simple solutions first, before pulling the car to pieces.

Never assume anything. Always check it yourself.


3. Consider the information and evidence gathered

What you have learned from your investigation and any tests you have carried out so far?

What things are not possible faults, based on the evidence?

What things could be causing the problem?

At this stage you have eliminated most of the possibilities, and have strong suspicions about one or two others. You may need to do some more tests, or partially dismantle a system, to finally identify the fault.

Example: The complaint is “overheating all the time”, and you have found that the vehicle recently had the head gasket replaced. You would probably do some more tests to see if a failure of that repair was causing the symptoms.

4. Locate the fault and its cause

If all has gone well you will now be able to confidently identify the faulty component or system.

Example: The engine is overheating, and the fault is “the cooling system passages are blocked with rust”.

4A. Feedback loop What caused the rust build‐up?

You suspect that the coolant and corrosion inhibitor is old, worn out, or at the wrong concentration.

A further test of the coolant should confirm this. You now know what the fault is, and what caused the fault.

5. Repair the fault and its cause

Decide on the most suitable repair to eliminate the fault.

Example: Thorough flushing and cleaning of the entire system, including blocked passages, replacement as required of welsh plugs and any other consumable items like hoses, and filling with new coolant.

In other cases there might be several equally valid alternatives.

Example: Overhaul the starter motor

OR fit a reconditioned change‐over unit

OR fit a brand‐new replacement.

Your choice might be influenced by such things as cost, time, complexity, or workplace policies.

6. Check all systems and confirm fault is fixed.

Check all related systems, as well as the faulty one, to confirm that:

the original symptoms are no longer present under any operating conditions, and

no other faults have been introduced.


Step 2 c) Gather information - Use other information sources Here is an example of the sort of information a workshop manual might provide:

Symptom Possible Fault

Engine overheats Loss of coolant

Belt tension incorrect

Radiator fins obstructed

Thermostat stuck closed

Cooling system passages blocked by rust, scale or other foreign material

Water pump not working‐ impeller loose, eroded

Thermo fan not working


Apply six-step diagnosis to a real problem Let’s apply this process to a diagnostic job mentioned earlier in this workbook ‐ the parking light not working.

Step 1

Confirm the symptom

Asked the customer to point out the light which is not working

Confirm that it is the left front parking lamp, and only the left front, which is not working

The symptom is real ‐ move on to Step 2.

Step 2

Gather information

a. Question the car’s owner about the park light’s use and behaviour up to the time of noticing the fault. Some sample questions and answers are in the table below this one.

b. Do the “look and feel” test. You find:

The park light is mounted firmly in the plastic front bumper.

The panel fit is good.

The bumper is not loose.

Looking behind the lamp, we can see that the wiring loom is intact and securely clipped to the bumper.

We remove the globe and inspect it ‐ sure enough, it’s blown!

But what causes globes to blow?


Step 2

Gather information – cont.

c. Use other information sources:

Even though we reckon we know this stuff, let’s check the workshop manual for any further information. The manual provides this chart:

Now that we have some reliable information, we can move on to Step 3.

Step 3

Consider the information and evidence gathered

What have we learned from our investigation so far?

Have we got enough information and evidence?

Can we confidently say what caused the globe to blow? Or can we at least narrow down the possibilities?

Let’s compare each of the possible causes from the workshop manual with the evidence and judge how likely each possible fault is.

Symptom Cause

Globe blown Old age ‐ very high number of on‐off cycles Vibration – loose lamp holder, loose panel mounting very rough roads Loose electrical connections – number of rapid on‐off cycles High circuit voltage – over stressed filament

Manufacturing defect


Feedback loop

Test 1 ‐ We need more information. Time to get the multimeter out!

Starting the engine and turning on the park light, we back‐probe the wiring connector at the faulty lamp with our multimeter set on the 20 volt range.

The result: 15.1 volts supplied to the light. Is this the right voltage?

Only one way to tell ‐ look it up in the workshop manual! The lighting circuit is part of the electrical circuit. The electrical circuit is supplied by the alternator.

According to the workshop manual ‐ Alternator regulated output voltage = 14.0 – 14.2 volts

Compare the measured circuit voltage with the manufacturer’s specifications ‐ it’s nearly a volt too high!

We can now say that the most likely cause of the blown globe is high circuit voltage, which over‐stressed the globe’s filament, causing early failure.

Test 2 ‐ We need to test the battery to make sure it hasn’t been damaged by over charging. Luckily it’s OK.

Step 4

Locate the fault and its cause

We now know the fault is a blown globe, and its cause is high circuit voltage which over‐stressed the globe’s filament.


Step 5

Repair the fault and its cause

The blown globe must be replaced with a new one.

The circuit voltage must be reduced to manufacturer’s specifications. Alternator output voltage on this car is set by the voltage regulator inside the alternator. The regulator needs to be replaced, but experience tells us that the alternator brushes will have suffered some natural wear as well.

We could:

overhaul the alternator in our workshop

fit a change‐over reconditioned unit supplied by the local auto electrician

fit a brand new unit supplied by the dealership.

Our recommended repair is to fit the reconditioned unit, which has been bench‐tested and is guaranteed. It is equivalent to the new unit, but is much cheaper. We won’t do the overhaul ourselves because our workshop is fully booked, and in any case we can’t do the job any cheaper than the reconditioned unit.

We should also advise the customer that all of the vehicle’s light globes have been stressed by excessive circuit voltage. In the interests of customer satisfaction, it would be wise to replace all of the safety‐related globes to avoid any subsequent “old‐age/ stress related” failures in the near future.

Step 6.

Check all systems and confirm fault is fixed.

We test all functions of the lighting system for correct operation, switching, illumination etc. Re‐check alternator regulated voltage, following manufacturer’s procedures.

The job is complete, apart from the paperwork.


Step 2 a. Gather information -Question the car’s owner What questions could we ask this customer?

Questions What information do we want? Answer

How often do you use the park lights? We want to judge how much service the light has given prior to failure

About 2 hours each week

What sort of driving do you do? We want to know if the car travels on rough roads a lot

Mostly city driving‐sealed roads

Has it ever stopped working before? To see if we’re chasing a recurring fault No

Have any other lights stopped working in the past?

To get a history of the car’s lighting problems Yes, a tail light and one headlight, at different times

What did you do about those failures? We want to know about any work done on the lighting system prior to this

A friend put new globes in‐ he said they were blown

Have you noticed anything else unusual about the operation of your car’s lights recently?

We want to know if there have been any other symptoms such as flickering, changes in brightness etc

No

Has any other work been done on the front end of the car recently?

This could point to problems created during an unrelated repair, such as panel damage

No


37

Activity 4

Question 1 A customer complains that his car’s engine “misses under load”. What could you do to confirm that this symptom exists?

_________________________________________________________________________________

_________________________________________________________________________________

_________________________________________________________________________________

Question 2 You need to get more information about the fault. Write down four useful diagnostic questions you could ask the owner.

1. ______________________________________________________________________________

2. ______________________________________________________________________________

3. ______________________________________________________________________________

4. ______________________________________________________________________________

Question 3 Choose a workshop manual and look up the manufacturer’s trouble shooting information for the symptom of “engine missing under load”.

OR choose a different symptom you would like to investigate.

Complete the table below by filling in the possible causes of this problem.

Symptom Possible causes


38

Question 4 The steps of a typical diagnostic procedure are set out below in boxes. Explain the purpose and importance of each step.

1. Confirm the symptom

Purpose _______________________________________________

_______________________________________________________

_______________________________________________________

_______________________________________________________

2. Gather information

Purpose _______________________________________________

_______________________________________________________

_______________________________________________________

_______________________________________________________

3. Consider the information and evidence gathered

Purpose _______________________________________________

_______________________________________________________

_______________________________________________________

_______________________________________________________

4. Locate the fault and its cause

Purpose _______________________________________________

_______________________________________________________

_______________________________________________________

_______________________________________________________

5. Repair the fault and its cause

Purpose _______________________________________________

_______________________________________________________

_______________________________________________________

_______________________________________________________

6. Check all systems and confirm fault is fixed.

Purpose _______________________________________________

_______________________________________________________

_______________________________________________________

_______________________________________________________


39

Question 5 Here are some questions you might ask a client to collect information about a vehicle problem.

Why would you ask each question? How could the customer’s answers help you to diagnose the problem?

a) “How often does the problem happen?”

_________________________________________________________________________________

_________________________________________________________________________________

b) “How old is the vehicle?”

_________________________________________________________________________________

_________________________________________________________________________________

c) “When does the problem occur?”

_________________________________________________________________________________

_________________________________________________________________________________

d) “Have you had any work done on the vehicle recently?”

_________________________________________________________________________________

_________________________________________________________________________________

e) “Do many different people drive the vehicle?”

_________________________________________________________________________________

_________________________________________________________________________________




40



41

Activity 5

Question 1 Create a diagnostic procedure for yourself in the space provided. Include the six steps you have learned about. Include all safety precautions necessary for safe work practices in your workplace.

You can design your procedure as a flow chart, or using dot‐points, as long as another person could easily follow your reasoning.

Remember to:

Ask questions and collect information

Think about all possible faults

Describe any tests you make

Recommend an appropriate repair.

The problem:

I’ve got a flat tyre!


42



43

Reporting and documenting diagnosis and repairs Often in an automotive workshop you will need to write things down, record them, and pass them on to other people.

This section deals with the documentation and reporting that may be required by diagnosis tasks.

Why do we need to document the diagnostic process? Recording information about a diagnostic procedure is important so that:

The technician can keep track of the process eg tests done and their results

The technician can see the build‐up of information which will help them eventually recognise the fault

The business can communicate accurately with the customer from the start of the diagnostic procedure until the repair is completed and paid for

The business can obtain authority to repair at the appropriate stages as the procedure is worked through

There is an accurate record if there is any dispute over the work done

There is a service record can be a helpful reference for future jobs.

The information should always be written down in an organised way so that anyone who looks at it can understand it. It is risky and bad practice to rely on your memory – the information needs to be written down, and not on a scrap of paper that can easily be lost or misplaced!

When a customer approaches a business for a fault to be diagnosed, most businesses set up a job card for the particular job. The job card becomes part of the vehicle’s service record, which is a file of information maintained by the workshop over time.


44

Set up a Job Card When a numbered Job Card or Repair Order is set up, you should record the following information:

Owner’s details

Car’s details

Customer’s concerns about the vehicle

Customer’s signature in the‘Authority to Repair’ space on the card.

The Authority to Repair is signed on the understanding that the customer will be consulted if the repair is going to be bigger or more expensive than first thought.

Example:

STEADY EDDIE REPAIRS

Job No. 1234 Date: 29/06/2010

Time: 08.45am

Service Adviser: L. Skywalker

Technician: A. Mechanic

Customer Name & Address:

A. Person

16 Long Street

Newburb VICTORIA 3999

Tel: 9123 4567

Year/ Make/ Model

2003 Daewoo Lanos

1.5 2dr Manual White

VIN No: KLATF08YE3B12345xxx

Engine No: A15SMS12345xxB

Customer Concern:

Radio loses station tuning presets

Kilometres: 165,732

Reg: ABC 123

Date & Time Promised: TBA

Authority to Repair: J Frost

Description of Work Carried Out


45

Gather information What questions would you (or another employee of the business) ask the customer?

Add this information onto the Job Card.

What checks would you do?

A “look and feel” check ‐ the radio is mounted firmly, and the connections are all secure.

After re‐tuning the radio, repeated starting and stopping of the engine eventually causes the symptom to re‐appear. By this time the cranking speed is noticeably slower than it was earlier.


Consider the information collected so far – what does it tell you?

The radio being made up of electronic components is a part of the electrical system, and so is the starter motor – could the problems be connected?

Another test is needed to measure voltage drop at the battery during cranking.

Car is seven years old.

Radio has been OK up until recently.

Once re‐tuned it works fine, only loses pre‐sets occasionally after engine starts.

Description of work carried out.

Visual inspection of radio & connections OK.

Re‐tuned OK.

Carried out multiple engine start‐stop, symptom returned (11th try).

Note ‐ cranking speed getting slower.


46

Feedback loop Use a multimeter to measure voltage drop at the battery during cranking. Voltage drops

to 9 volts ‐ it looks like the battery is faulty, and the low voltage is causing the radio to lose its memory during cranking.

A specific gravity test of the electrolyte is good.

A battery capacity test shows that the battery capacity is now less than half what it was when it was new, which accounts for the slower cranking speed.

A double‐check of starter current draw (80A), using a good slave battery, shows that the excessive voltage drop is not being caused by the starter circuit. Alternator output measures 14.4 volts at 50 amps, which is within specifications.

Identify the fault and its cause The technician is now confident that the faulty battery is the cause of the problem, and updates the diagnosis record:


The technician has to stop here and clock off.

Description of work carried out


Re‐tuned OK.



Battery connections OK.

Spec Grav = 1.265

Cranking voltage = 9V.

Starter draw= 80A at 11 volts using slave battery.

Charging voltage 14.4V @ 50A.

Battery capacity 40%.

Time on 09.35 am

Time off 10.10 am

Parts


47

Someone must contact the customer and tell them that a new battery is needed, to avoid any misunderstanding later. The customer must agree to this repair, perhaps in writing.


Repair the fault and its cause The technician can clock back on to the job and finish the repair:

Fit a new battery

Re‐tune the radio to preferred stations.

Check all systems and confirm fault is fixed Check all electrical systems for correct operation. The battery is put under load by turning on headlights, heated rear screen, air conditioning etc and at the same time repeatedly operating the starter motor.

The radio does not lose its pre‐set tuning, confirming that the fault is fixed.

The last tasks for the technician are to:

Make sure that no dirty marks have been left anywhere on the car.

Park the car in the appropriate spot.

Return the driver’s seat to its original position, if it has been moved.

Authority to Repair

Repairs to radio

Signature……J. Frost … Date…29/06/10

OR via Telephone:

Time received:…08.50 am

Email:

Fax:

Additional Work ‐ Authority to Repair

Fit new battery

Signature …………...............…..

Date:…29/06/10

OR via Telephone:

Time received: 10.30 am

Email:

Fax:


48


Then pass the Job Card on to Reception for processing.

Reception will:

prepare the invoice for the customer

inform them that the car is ready

carry out the hand‐over when the customer arrives

explain any aspects of the repair as required

taking payment.

Description of work carried out


Re‐tuned OK.



Battery connections OK.

Spec Grav = 1.265

Cranking voltage = 9V.

Starter draw = 80A at 11 volts using slave battery.

Charging voltage 14.4V @ 50A.

Battery capacity 40%.

Battery is faulty

Repair

Fitted new battery

Re‐tuned radio to customer’s stations

Tested for loss of pre‐sets

System operation correct.

Time on 09.35 am

Time off 10.10 am

Time on 10.40 am

Time off 11.30 am

Parts

N480ZZ battery


49

Activity 6

Fill out the Job Card on the next page.

Use the information from the diagnosis task detailed in the section Applying these six diagnostic steps to a real problem earlier in this workbook.

Find and use the VIN and engine numbers of any training vehicle in the workshop.

If a vehicle is not available, you can make these numbers up.

Make up the customer’s name and address.

My parking light

isn’t working.


50

STEADY EDDIE REPAIRS

Job No. 1235 Date:…………….............…

Time: ………………............

Service Adviser: ………........………..................…..

Technician: …………………….........................…..

Customer Name & Address

Tel:

Year/ Make/ Model

……………………………………...….............................…

Reg. No. ………………………………….…………………….…

VIN No. ………………….…………….……………………….…

Engine No. ………………..……………………………...….…

Customer Concern:

Kilometres …………….

Authority to Repair

Signature: .................... ………………

Date: …../….../.......

Date & Time Promised: TBA

Description of Work Carried Out:

Time on Time off

Parts Cost


51

Authority to Repair

………………………………………………..

Signature: .........................................………….

Date: …../…./……..

OR via Telephone: ..........................

Time received: ………………...

Email:

Fax:

Additional Work‐ Authority to Repair

………………………………………………..

Signature: ……….................................….

Date: …../…./……..

OR via Telephone ...........................

Time received: ………………...

Email:

Fax:




52



53

Writing a diagnostic report When might you have to write a report on work you have done?

insurance repairs ‐ where the insurer wants to know exactly what was done

disputes about repair work ‐ a lawyer might want a written report about work done

careful owners ‐ who want a written record of what was done to their vehicle

warranty work for another repairer or car dealer ‐ eg when an interstate visitor breaks down, and your workshop carries out repairs on behalf of a third party

research work ‐ especially if you work in the development (experimental) area of a vehicle manufacturer.

Why is it important to write a report in a standard way?

It helps to make sure that:

all the important parts of the work are covered

another person can understand what has been done

another technician can repeat your work if necessary (if it is part of a research or development project).

The following section suggests the main headings that a report might contain.


54

Parts of a Report Contents

Useful for longer reports ( more than a few pages)

Helps a reader to quickly find what they want.

Introduction

Explains the reason for writing the report (why was the report requested? Who asked for it?)

Summarises the symptom and task that the report covers.

Procedure

Explains exactly what was done during the diagnosis and repair. Don’t leave out anything important

Identify any special test equipment used

A description of the conditions under which a test was done eg ambient temperature and humidity for a performance test on a vehicle’s air conditioning system.

Results of tests and investigations

Record measured test results

A report on component condition (serviceability)

Might give details of specific test procedure/s, if that could affect the test outcome eg measuring a/c pressures with or without a workshop fan in front of the condenser.

Conclusion

Explain what you have discovered/ observed/ concluded from your investigation of the problem

What you believe caused the problem

What you have done to repair it

If you haven’t solved the problem, explain why.

Recommendations

Recommend any further action you believe is needed to make sure the problem stays fixed (eg if you have just replaced an air filter element blocked with dust from unmade country roads, you might advise that the service intervals for the vehicle should be shortened from 10,000km to 5,000 km.)


55

I’ve checked my records and the old battery was still covered by warranty. Could you give me a written report of the work done, so that I can show the supplier of the old battery that it was actually faulty? Then I can claim against the warranty.

An example of a report This report was written for the job described just a little earlier where the radio kept losing its tuning pre‐sets and the battery was replaced.

On the next page is the technician’s report. There is no contents page, because it’s quite short:


56

Report on Job No. 1234 - Radio losing tuning pre-sets Introduction

Report for Mr. A Person, owner of Daewoo Lanos, reg no. ABC 123, VIN KLATF08YE3B12345xxx. Re: diagnosis and repair of the fault responsible for the following symptom: Radio loses tuning pre‐sets intermittently.

Procedure

Vehicle delivered with radio un‐tuned (pre‐sets had been lost). Owner said he could re‐tune the radio but the settings would be lost at irregular intervals, but only after an engine start.

Technician carried out the following checks:

Re‐tuned radio without difficulty, and checked for normal operation‐ it performed correctly.

Visual inspection of radio and harness after re‐tuning ‐ no fault found.

Wriggle test in an attempt to re‐create the problem‐ no fault found.

A series of engine re‐starts. After the 11th re‐start, the radio had lost its tuning pre‐sets. Cranking speed was slower than normal, so battery volt‐drop suspected as the cause of the problem.

A cranking voltage test indicated a battery problem, although a hydrometer test showed it to be fully charged.

Starter current draw was tested using a good slave battery, and alternator output was measured. Both were found to be within specifications.

A battery capacity test indicated a faulty battery. The battery was replaced with a newN480ZZ.


Operation of re‐tuned radio normal

Visual check no faults found

Wriggle test no faults found

Cranking voltage drop 10 volts‐ LOW

Starter current draw 80 amps‐ OK

Alternator output 14.4 volts @ 50 amps‐ OK

Battery specific gravity 12.65‐ OK

Battery capacity test 40%‐ faulty

Diagnosis

Inspection and testing of the systems connected with the radio showed that the radio circuit was operational, but that a faulty battery suffered excessive voltage drop on starting, leading to radio memory loss.

Repair

A new battery fixed the problem. Repetition of the start, re‐start test confirmed the fault was eliminated.

Recommendations

That this vehicle be regularly serviced, with special attention to regular checks of battery electrolyte, terminal cleanliness, and mounting security to maximise battery service life.


57

Activity 7

Write a report on a diagnosis and repair for a ‘third party’. This could be anyone outside of the repair business ‐ perhaps an insurance company or the manager of a vehicle fleet.

Base the report on the same repair you wrote the job card for in Activity 6 – “parking light not working”. Use the information from that section to write your report.

The report form is on the next page.

Hints

Don’t bother with a contents page‐ your report won’t be that long!

Use the headings A to E provided.

Write in brief points – it’s not an essay! ‐ but include all important details.


58

STEADY EDDIE REPAIRS Diagnostic Report on Job No. 5678

Introduction

Procedure


Conclusion

Recommendations




59

Other diagnostic approaches Branching diagnostic procedures

The diagnostic procedures discussed previously are all linear – that is, each step must be completed before you can do the next one. This approach works well for many vehicle faults, especially where the technician only has to deal with one or two systems.

When a fault occurs in a more complex system, or in a system which has connections to other systems, a branching diagnostic procedure might be used. This requires the technician to make “yes / no” or “good / bad” decisions about various components or functions of a system.

It is sometimes called a “decision tree” or a “trouble tree”.

These procedures are sometimes provided by manufacturers in their workshop manuals. If the procedure is followed correctly, the technician will eventually diagnose the faulty component and be able to complete the repair.

Example: Part of a diagnostic procedure for checking a lubrication system

Figure 6: Branching diagnostic procedure

N

Oil level correct?

Pressure correct at 250‐280 kPa?

Pressure too low

Pressure too high

Clean/replace filter, recheck pressure

Check for restrictions


60

Benefits of this procedure The branched diagnostic procedure can speed up diagnosis.

As you gather your evidence, the procedure sets out the possible problems, and directs you to the next question or test. Decision making is reduced to simple yes / no questions.

In modern vehicles, with multiple ECUs and bus communication systems, there is a high level of interconnection between systems, and these procedures help you find your way logically through the maze.

However, the technician’s skill and knowledge is still essential for testing or evaluation of components.

CAUTION! Be cautious when using a manufacturer’s branching diagnostic procedure. There could be errors in the process so you shouldn’t just follow it blindly.

As you work through the process, ask yourself if what you are doing is logical and in the right order, and if the specifications quoted sound sensible.

Also, they can’t take into account all the factors which are outside the system, but which could still affect it. So you must keep these in mind yourself.


61

Activity 8

Branched Diagnostic Procedures Design a simple “decision tree” (branched diagnostic procedure) for the symptom described below.

Make it simple and clear so that any other technician to follow your process.

Assume that the symptom has already been confirmed.

Vehicle: 2004 base model 4 cylinder Korean import, manual transmission.

You could start with this step:

My car has been losing coolant. I have to put in almost half a litre every week!

Visually inspect cooling system ‐ evidence of leaks?

YES NO


62

Sketch your decision tree here.



Visually inspect cooling system ‐ evidence of leaks?

YES NO


63

‘Black Box’ Diagnosis Most vehicle systems now include an electronic control unit (ECU) as a master control unit. The ECU is too complex to be repaired by the average workshop, but its functions can be fairly easily understood. It is called a ‘black box’ because we know what the ECU does, but we don’t know (and don’t need to know) how it does it.

Example:

Figure 7: Diagram of a black box system

This diagram is a simple picture of a typical vehicle electrical or electronic system. The ECU is at the centre, with a control job to do.

The ECU receives information (‘inputs’) from a variety of sensors which are connected to the ECU by wires.

The ECU processes the inputs through its internal programming (which we don’t need to know about).

Then it sends commands (‘outputs’) to external devices (‘actuators’) to carry out specific actions. These actuators are also connected by wires to the ECU.

Sensors measure things like coolant temperature, manifold air temperature throttle position, engine rpm, crank angle and road speed.

Actuators are used to control things like alter idle speed, ignition control, fuel injectors and EGR control (Exhaust Gas Recirculation)

Sensors send inputs to ECU

ECU sends outputs to actuators


64

What if the fault is in the black box? Most vehicle ECUs are very reliable, but occasional failures can be caused by:

dry solder joints on circuit boards

water leaks, or

“zapping” by electrical spikes such as those caused by careless welding on the vehicle.

It is more likely that the sensors or actuators will develop faults. These faults can be found by the normal diagnostic techniques described earlier. The ECU itself may be capable of testing whether there are faults in the inputs or outputs.

If all of the sensors, actuators, connections, power supplies and earths connected to the ECU are working, then the fault must be in the ECU itself.

CAUTION: If all of your tests suggest that the ECU is faulty, re‐check, then RE‐CHECK again. ECUs can be very expensive


65

On-Board Diagnostics All new cars sold in Australia from 2006 onwards must have On‐Board Diagnostics (OBD). The

current system is version number two and is referred to as OBD 2. All manufacturers must

use the same basic system. Before this, many vehicles had some form of on‐board

diagnostics, but each manufacturer had a different system.

What is OBD 2? OBD 2 is designed to self‐diagnose and report when a vehicle’s emission control system fails to meet, or is likely to fail to meet, legal requirements for vehicle emissions.

OBD 2 is a universal system:

All manufacturers must use it

All manufacturers must use the same code numbers for the same emission‐related faults

All cars must have the same data link connector

It must be easily accessible within about 600 mm of the driver’s seat ‐ near the steering column, or in the centre console.

All manufacturers must use the same communication protocol to allow access to the DTCs

The emission‐related codes must be accessible to any generic scan tool.

How does an OBD system help with diagnostics? OBD systems are a valuable source of information. When a technician is gathering information early in the diagnostic procedure, a vehicle with OBD can save a lot of time by providing some of that information ‐ how much, depends on how sophisticated the system is.

The first OBD systems often used a warning light on the instrument panel sometimes called a ‘Malfunction Indicator Light’ or a ‘Check Engine Light’.


66

Figure 8: Location of malfunction indicator light

This light could be made to blink or flash out a number code which could then be matched to the manufacturer’s list of possible faults. The number code is called a Diagnostic Trouble Code.

Example:

Figure 9: Coded lights

Malfunction Indicator light

VT Holden Data

Link Connector


67

Example: Some of the Diagnostic Trouble Codes for a Holden VT 3.8 litre V6.

Some of these codes will turn on the ‘Check Engine’ light; others will not. See the workshop manual for details.

To display the VT Holden codes:

switch OFF ignition and all accessories

bridge terminals 5 and 6 of the Data Link Connector located near the steering column

The ‘Check Powertrain’ light will then flash out any DTC codes, beginning with DTC 12 (because the engine is not running).

VT Holden V6 3.8 litre

12 No RPM signal 13 Right Hand (RH) No Oxygen Sensor Signal 14 Engine Coolant Temperature ECT ‐ Signal Voltage Low 15 Engine Coolant Temperature ECT ‐ Signal Voltage High 16 Engine Coolant Temperature ECT ‐ Signal Voltage Unstable 17 PCM Error ‐ ECT Circuit 18 EGR Flow Fault 19 Throttle Position (TP) Sensor Stuck 21 Throttle Position (TP) ‐ Signal Voltage High 22 Throttle Position (TP) ‐ Signal Voltage Low 23 Intake Air Temperature (IAT) ‐ Signal Voltage High 24 No Vehicle Speed Sensor Signal ‐ Auto Transmission 25 Intake Air Temperature (IAT) ‐ Signal Voltage Low 26 Intake Air Temperature (IAT) ‐ Signal Voltage Unstable 43 Knock Sensor Circuit Fault 44 Right Hand (RH) Lean Exhaust Indication 45 Right Hand (RH) Rich Exhaust Indication 46 No Reference Pulses While Cranking 47 18X Reference Signal Missing 48 Camshaft Position Signal Missing 49 Cam/Crank Signal Intermittent 63 Left Hand (LH) No Oxygen Sensor Signal 64 Left Hand (LH) Lean Exhaust Indication 65 Left Hand (LH) Rich Exhaust Indication 76 Short Term Fuel Trim (STFT) Delta High 78 Long Term Fuel Trim (LTFT) Delta High 96 AlC Pressure Sensor Fault 97 Canister Purge Circuit Fault


68

Reading codes and information with a scan tool A scan tool or code reader is a device which plugs into the data link connector. It can:

access the vehicle’s ECU

display the DTCs on a small screen

clear codes from the ECU’s memory.

As manufacturers developed their own particular on‐board diagnostics systems, they also developed their own special scan tools to read their system. For example, a Holden dealer would use Holden’s own Tech 2 scan tool to display and clear the codes listed above.

As OBD systems developed they became too complicated to continue using the flashing method of code reading, and now the only way of accessing the codes is with a scan tool.

Figure 10: Reading codes with a scan tool


69

Proprietary and generic scan tools Manufacturer’s scan tools are known as ‘proprietary’ or ‘genuine’ scan tools. They are usually only available within the dealer network. Independent automotive businesses cannot buy these tools.

Genuine scan tools These can usually do more than just read DTCs. They may be able to:

allow the technician to see more information, such as the vehicle’s VIN

allow the technician to test the operation of output devices or actuators, such as cooling fans, fuel pumps, window motors etc.

display a direct read‐out of actual live data, such as current coolant temperature, throttle position, or air conditioning pressure

upload new software to ECUs

carry out tasks such as programming replacement keys.

The trend amongst manufacturers now is to use a combined diagnostic and information system.

The vehicle is connected to a dedicated computer rather than to a hand‐held scanner. The computer is better able to deal with the highly sophisticated current OBD 2 systems. It may be able to directly access a database which could include a digital workshop manual, diagnostic flow charts and service bulletins. This information could speed up diagnosis.

Generic scan tools These are generally less capable than the genuine types but are still extremely valuable for extracting trouble codes and some live data. They are easily available from equipment suppliers.

Their capabilities can range from a basic code reader that simply displays a numeric code, to scanners which almost match the genuine scan tool in usefulness. Most generic scan tools provide adaptors (if needed) for the Data Link Connector, and either on‐board software or cartridges to allow the scanner to communicate with a wide range of vehicles.


70

What information is available from an OBD system? Early OBDs focussed on faults related to the powertrain (engine and transmission) and emission controls. As they became more sophisticated, the amount and type of information expanded.

The modern OBD 2 systems can:

show live or current data (the actual values right now for various components, such as air flow rate, current RPM, or ignition timing)

show ‘freeze frame’ data (the information captured by sensorsat the time the fault occurred)

show stored Diagnostic Trouble Codes

show pending Diagnostic Trouble Codes (detected during current or last driving cycle)

clear Diagnostic Trouble Codes and stored values

test results, oxygen sensor monitoring (non Controller Area Network [CAN] only)

test results, other component/system monitoring (Test results, oxygen sensor monitoring for Controller Area Network [CAN] only)

control operation of on‐board components/ systems

request vehicle information.

Essential features of an OBD 2 system Check Engine light The system will verify a fault before turning on the light. A detected fault is stored as a pending fault. If the same fault occurs on the next two driving cycles, the light will be turned on and the fault is stored as a confirmed fault. The light may be turned off again if that fault doesn’t happen again during the next three driving cycles.


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Freeze Frame information When a fault is first detected, the system must store at least the following information:

the fault code for the event that prompted the data to be stored

coolant temperature

engine speed

engine load

fuel pressure, if available

inlet manifold pressure, if available

fuel trim values, if available

open or closed loop operation

vehicle speed, if available.

Readiness testing The system monitors and tests all emission‐related components or systems during a specified drive cycle. The ECU reports ‘Ready’ or ‘Not Ready’ for those systems when a scan tool is connected.

Some systems are monitored continuously, such as engine misfiring and evaporative emissions. Other systems are monitored, but not continuously, such as the EGR, catalytic converter, air conditioning etc.

During these tests the system may turn various sensors and actuators on or off to see what effect is produced, and compare that effect with the expected result. Any variation outside of the programmed limits will set a diagnostic trouble code.

Diagnostic Trouble Codes a. Mandated codes For any emission‐related system, the codes are provided by the government and must be used no matter what make the car is. The codes must be accessible by any OBD 2 scan tool.

The codes must have a letter followed by four numbers, like this: P0105. The meaning of the code is the same for all manufacturers. In this case, P0105 means ‘Manifold Absolute Pressure/Barometric Pressure Circuit Malfunction’, no matter what make of car it is.

b. Manufacturers’ codes For any other system, like ABS, manufacturers can make up their own DTCs and they are not obliged to give code access to non‐proprietary scan tools (though many do).


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How OBD 2 codes work There are probably thousands of possible OBD 2 codes. This is the way they are created.

P 0 1 15

Which vehicle system triggered the code?

Is the code mandated or a manufacturer’s own code?

What sub‐system is associated with the fault?

Gives more detail of the fault

P= Powertrain system

B= Body system

C= Chassis system

U= Unused, or sometimes communication faults

0 = Mandated code (emissions)

1 = Enhanced OBD 2 code available for use by any vehicle maker

1 = Fuel and air metering

2 = Fuel and air (injection circuit)

3 = Ignition or misfire

4 = Auxiliary emission controls

5 = Vehicle speed and idle control

6 = Transmission

Many possibilities

P0115 is a powertrain problem

P0115 is a mandated code.

P0115 is a fault which affects fuel and/or air metering

15 indicates a fault in the Coolant Temperature circuit, which would affect fuelling

Vehicle System codes

P codes‐ Power train means engine and transmission sub‐systems.

B codes‐ Body control systems like lighting, air conditioning, audio etc.

C codes‐ Chassis control systems like ABS, ESP, active suspension, traction control etc.

Enhanced OBD 2 code ‐ it is the manufacturer’s choice to make it available to a scan tool


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Body and Chassis Codes Examples: B0540 Speedo signal error (used by any / all manufacturers) C0035 LHF wheel speed signal error (used by Holden)

Below is a sample list of OBD 2 ‘P’ codes:

These are just a few of the many codes possible.

You can see that there is an enormous amount of information that could be available to a technician trying to diagnose a fault.

How much information you can actually get depends on which codes the manufacturer has decided to use, and whether the maker has given free access to any non‐ mandated, vehicle specific codes as well.

P0010 A Camshaft Position Actuator Circuit (Bank 1) P0011 A Camshaft Position ‐ Timing Over ‐ Advanced or System Performance (Bank 1) P0012 A Camshaft Position ‐ Timing Over ‐ Retarded (Bank 1) P0013 B Camshaft Position ‐ Actuator Circuit (Bank 1) P0014 B Camshaft Position ‐ Timing Over ‐ Advanced or System Performance (Bank 1) P0015 B Camshaft Position ‐ Timing Over ‐ Retarded (Bank 1)

P0024 B Camshaft Position ‐ Timing Over ‐ Advanced or System Performance (Bank 2) P0025 B Camshaft Position ‐ Timing Over ‐ Retarded (Bank 2) P0026 Intake Valve Control Solenoid Circuit Range/Performance (Bank 1) P0027 Exhaust Valve Control Solenoid Circuit Range/Performance (Bank 1) P0028 Intake Valve Control Solenoid Circuit Range/Performance (Bank 2) P0029 Exhaust Valve Control Solenoid Circuit Range/Performance (Bank 2)

P0068 MAP/MAF ‐ Throttle Position Correlation P0069 Manifold Absolute Pressure ‐ Barometric Pressure Correlation P0070 Ambient Air Temperature Sensor Circuit P0071 Ambient Air Temperature Sensor Range/Performance P0072 Ambient Air Temperature Sensor Circuit Low P0073 Ambient Air Temperature Sensor Circuit High P0074 Ambient Air Temperature Sensor Circuit Intermittent

P0095 Intake Air Temperature Sensor 2 Circuit P0096 Intake Air Temperature Sensor 2 Circuit Range/Performance P0097 Intake Air Temperature Sensor 2 Circuit Low P0098 Intake Air Temperature Sensor 2 Circuit High P0099 Intake Air Temperature Sensor 2 Circuit Intermittent/Erratic


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Activity 9

Tick the correct answer/s. There may be more than one.

Question 1 When using ‘black box’ diagnosis to find a fault, the technician must:

Replace any ECUs which are not coloured black

Test no more than three of the inputs to the ECU

Test all of the sensors, actuators, power supplies and earths connected to the black box

Open the black box and probe the circuit boards with a Phillips screwdriver.

Question 2 When discussing vehicle faults, the term ‘OBD’ means:

Out Board Depth

One Bad Device

On Board Diagnostics

Own Brand Diagnostics.

Question 3 What is OBD 2?

A compulsory on‐board diagnostic system for all new cars since 2006

A voluntary on‐board diagnostic system for all new cars since 2006

An on‐board diagnostic system accessible by any OBD 2 scan tool

An on‐board diagnostic system aimed at monitoring vehicle emissions.


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Question 4 The purpose of an OBD system is to:

Detect faults in vehicle systems and immobilize the vehicle until repairs are made

Detect faults in vehicle systems and alert the driver

Detect faults in vehicle systems and automatically fix the problem

Detect faults in vehicle systems and tell the technician where to look for faults.

Question 5 When a fault is detected in a vehicle system, the driver is alerted by:

An SMS message

E‐mail

Malfunction indicator light

A voice message through the audio system.

Question 6 An OBD 2 system should be able to:

Show current data

Show ‘freeze frame’ data

Show stored Diagnostic Trouble Codes

Clear Diagnostic Trouble Codes and stored values

Show pending Diagnostic Trouble Codes.

Question 7 A ‘pending’ OBD 2 code is one which:

Does not turn on the ‘Check Engine’ light

Is set when a fault occurs once, but doesn’t appear again

Depends on the make of vehicle

Relates only to suspension systems.


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Question 8 ‘Freeze frame’ data is:

The information captured by the ECU when a DTC occurred

Information that relates only to the climate control system

The data the system’s sensors were providing at the time a fault occurred

Information provided when the engine seizes.

Question 9 ‘Live data’ is:

Only available if the technician is in the driver’s seat

The actual operating values for various parts of an operating system e.g. voltage

Provided only for components which have movement e.g. windscreen wipers

Available from any live electrical connection e.g. the positive battery terminal.

Question 10 What do these OBD 2 codes mean?

P0442

P0074

P0013

P0103

P0205




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Activity 10

Ask your teacher to direct you to a vehicle or a system with a fault. Use any of the methods described in this workbook, OR any other method available to you to diagnose the fault in the vehicle or system.

You may use workshop manuals supplied by your teacher; textbooks; commercial information sources; service bulletins; test equipment or scan tools to help you.

Remember to check the workshop manual for any suggested diagnostic approaches.

As you work through the diagnosis, record the steps you take and the results of any tests you make. The record can be in the form of a step‐by‐step procedure, or it could be a ‘decision tree’.

Observe all relevant safety precautions while working.

Good luck!




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Glossary WORD MEANING

abnormal Things are NOT okay, or NOT the way they should be

abnormal event When something happens NOT in the way it should

accurate Correct, exact

actuators Devices which carry out specific actions

confirm Check that something is true

confirmed Definite

data Information

diagnosis Finding the cause of a problem

efficient Doing things well in the quickest time possible

eliminate Get rid of

event Something that happens

fault Problem

faulty Worn, broken, not working correctly

feedback loop When you get some information from a check or test, you use it to rethink what you will do next.

‘freeze frame’ data Information which shows exactly what data the system’s sensors were providing at the time the fault occurred

hazard Danger

inefficient Taking longer than necessary to do something

input Information going into a system

live data Information from right now, such as current coolant temperature, throttle position, or air conditioning pressure

logical Sensible


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WORD MEANING

mandated Required by law

minimum Least

normal Things are okay or the way they should be

normal event When something happens in exactly the way it should

output Command or message going out

pending Waiting

procedure A logical set of steps to follow

productivity Time spent per job

proprietary Owned by the manufacturer

subsequent Later

symptom A clue that something is wrong.

systematic Following a sensible order or system, not just any way it happens

third party First party ‐ the car owner

Second party ‐the repair business

Third party – someone else eg an insurance company, or the manager of a vehicle fleet

valid True

ventilation Fresh air

warranty Manufacturer’s promise to replace a faulty item

Documents

AURT366108A LWB Word - Learning Research & …lrd.kangan.edu.au/.../AURT366108A/AURT366108A_LWB_PDF.pdfBatteries Batteries contain sulphuric acid (H2SO4). Battery acid will destroy