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23-04-27Info class Internal ETDP/sssszf/CAN bus properties

CAN bus properties

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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CAN networks on PGRT

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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CAN message

Bus idle Bus idle

Start of frame

Arbitration field

Control field

Data field

CRC error check field

Acknowledgement field

End of frame

IntermissionIdentifier

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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Achieving the electrical bit

4V 2.5V 2.5V 1V

0 CAN high 1

0 CAN low 1

Time

Vol

tage

tran

smitt

ed

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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Signal properties of a CAN bus

Recessive signal

Dominant signal

120 Ω

120 Ω

ECU

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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Visualized with a Scope meterCAN_H

average voltage CAN_L average

voltage

CAN_L lowest peak voltage

CAN_H highest peak voltage

Recessive signal level

Dominant signal level

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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ECU electronic principle

Voltage converter

Power mode logic

Analogue inputs

Digital inputs

Digital outputs Drivers

Sensors Actuators High current actuators

Transceiver

CPU-module

CAN bus

Power supply

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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Transceiver components

CAN bus

PNP

NPN

Inverter

Comparator

Resistor network

CAN Controller

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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Transceiver function

CAN bus

0

+ _

0

CAN Controller

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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Transceiver function

1

+_

1

CAN Controller

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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Messages types: point to point

ECU ECU ECU ECU

ECU ECU ECU

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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Messages types: broadcast

ECU ECU ECU ECU

ECU ECU ECU

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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CAN bus without terminal resistors

ECU ECU ECU ECU

ECU ECU ECU

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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CAN bus with terminal resistors

ECU ECU ECU ECU

ECU ECU ECU

Type of resistor mount it on the CAN connector block

Type of resistor- capacitor assy mount it into an ECU

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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Red, Green and Yellow bus connector blocks

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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Lowest possible specification

Enginemanagement

Visibility

Instrumentcluster

Yellowbus

Red bus

GREEN CAN BUS

Diagnostic connector

COO

COO

EMS

ICL

VIS

Yellow CAN BUS

RED CAN BUS

DIAGNOSTICS (SDP3)

APS

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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Termination resistors

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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Troubleshooting CAN buses

Scania multimeter 588 094 measure the integrity of the CAN wires and the CAN voltage levels: Measuring CAN bus resistance: able to trace wire and

termination resistors faults; able to trace open circuits or short circuit to ground or ECU’s internal supply (internal converter supplies with 5V).

Measuring CAN bus voltage: able to trace ECU’s internal faults or wire and termination resistors faults.

CAN messages can not be checked with a multimeter; instead the diagnose software is used to check the systems functionalities.

WSM 16:07-02 “Communication problems” shows measuring methods

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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Measuring resistance

+15 OFF

31

CAN_H

CAN_L

60 Ω120 Ω

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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Measuring resistance

+15 OFF

31

CAN_H

CAN_L

>1 kΩ

23-04-27Info class Internal ETDP/sssszf/CAN bus properties

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Measuring voltage

+15 ON

31

CAN_H

CAN_L

~2.6V~2.4V