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LAB SCOPE
• PULSE WIDTH (P.W.) IS THE TIME THE CIRCUIT IS ON, COMPLETING ITS PATH TO GROUND
• MEASURED IN MILLISECONDS (m.s.)
• MEASURED FROM THE BEGINNING OF ON TO THE END OF ON
LAB SCOPE
• FREQUENCY (Hz) IS THE NUMBER OF TIMES SOMETHING OCCURS WITH IN ONE SECOND
• MEASURED IN HERTZ (Hz)
6
LAB SCOPE
0 10 20 30 40 50 60 70 80 90 1 10 20 30 40 50 60 70 80 90 2MILLISECONDS
FREQUENCY
2 OCCURENCES EVERY SECOND EQUALS 2 Hz
LAB SCOPE
• TO TEST A SENSOR, BACK PROBE THE SENSOR SIGNAL RETURN WIRE
• TO TEST AN ACTUATOR, BACK PROBE THE COMPUTER CONTROLLED GROUND
LAB SCOPE
• NOISE IN A WAVE FORM CAN BE CAUSED BY AN OUTSIDE SOURCE OR MAGNETIC FIELD
• ALWAYS USE THE SCOPES CHASSIS GROUND AND HOOK IT TO THE ENGINE BLOCK
• KEEP THE SCOPE LEADS AWAY FROM ELECTRICAL DEVISES
17
GOOD PATTERN
BAD PATTERN
BAD PATTERN
BAD PATTERN
OPEN IN SENSOR RESISTOR
LOW RESISTANCE IN SENSOR
HIGH RESISTANCE IN SENSOR
19
GOOD PATTERN
GOOD PATTERN
BAD PATTERN
BAD PATTERN
SIGNATURE PROFILE PIP #1 TDC
AS LOAD OR SPEED INCREASE, Hz INCREASE
TIME CHANGE WITHOUT LOAD CHANGE
OFF SIGNAL CRASH
22
GOOD PATTERN
GOOD PATTERN
GOOD PATTERN
BAD PATTERN
NARROW P.W. - LEAN WIDE P.W. - RICH
LOW FREQUENCY HIGH FREQUENCY LEAN RICH
LOOSE VOLTAGE WIRE
25
GOOD PATTERN
BAD PATTERN
BAD PATTERN
BAD PATTERN
BAD PATTERN
BOUNCING BRUSH
POSITIVE DIODE SPIKE
NEGATIVE DIODE SPIKE
OPEN DIODE
LESS THAN 100ms
O2 SENSOR MUST SWITCH RICH TO LEAN AND LEAN TO RICH IN LESS THAN 100ms FOR CATALYST TO OPERATE
TEST AT 2000 RPM ENGINE AT OPERATING TEMPERATURE
O2 SENSOR TEST
31
PERCEPTION SCOPE - SECONDARY IGNITION TEST
• ENGINE HOT
• 1000 RPM
• SPECIFICATIONS– BURN kV = 1.1 kV TO 2.1 kV– BURN TIME = 1.0 ms TO 1.8 ms– FIRING kV =
• 7.5 kV TO 12 kV DISTRIBUTER • 5 kV TO 12 kV DIS
32
GOOD - PATTERNTURBULENCE, INTAKE VALVE, CARBON ON INTAKE VALVE, CARBON ON PLUG
FOULED PLUG - CARBON LOW COMPRESSION
33
EXHAUST VALVE INTAKE VALVE, LEAN MISFIRE
FOULED PLUG - OIL, FUEL, CARBON
FUEL FOWLING, RICH CONDITION - CONDENSING AT CYLINDER WALLS
35
TROUBLE TREE CHART
STEP A:
TO TEST ALL CIRCUITS AND THE SENSOR.
BACK PROBE SIGNAL RETURN AT THE PCM.
NO PROBLEM - CIRCUIT OK
YES PROBLEM - GO TO STEP B
37
TROUBLE TREE CHARTSTEP B:
TO TEST SENSOR, 5 VOLT AND GROUND CIRCUIT.
BACK PROBE SIGNAL RETURN AT THE SENSOR.
NO PROBLEM - REPAIR SIGNAL RETURN CIRCUIT
YES PROBLEM -ANALOG SENSOR - GO TO STEP C
DIGITAL SENSOR - GO TO STEP D
39
TROUBLE TREE CHART
STEP C:
ANALOG SENSOR
TO TEST 5 VOLT AND GROUND CIRCUIT.
BACK PROBE 5 VOLT AND GROUND CIRCUIT.
NO PROBLEM - REPLACE SENSOR
YES PROBLEM - REPAIR 5 VOLT OR GROUND CIRCUIT
41
TROUBLE TREE CHARTSTEP D:
DIGITAL SENSOR
THREE AREAS
A - VOLTAGE SUPPLY CIRCUIT (PROBLEMS - REPAIR CIRCUIT)
B - SENSOR(PROBLEMS - REPLACE SENSOR)
C - GROUND CIRCUIT(PROBLEMS - REPAIR CIRCUIT)