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INSPECTION PROCEDURE USING AN OSCILLOSCOPE
 
 
CAMSHAFT POSITION SENSOR AND CRANKSHAFT POSITION SENSOR
Required Special Tools:
  • MB991709: Test Harness
  • MB992110: Power Plant ECU Check Harness
 
 
Measurement Method
1. Disconnect the camshaft position sensor connector, and connect the test harness special tool (MB991709) between the separated connector (All terminals should be connected).
2. Connect the oscilloscope probe to intake camshaft position sensor connector terminal No. 3.
3. Disconnect the crankshaft position sensor connector, and connect the test harness special tool (MB991709) between the separated connector (All terminals should be connected).
4. Connect the oscilloscope probe to crankshaft position sensor connector terminal No. 3.

 
 
Alternate method
1. Disconnect all ECM connectors. Connect the check harness special tool (MB992110) between the separated connectors.
2. Connect the oscilloscope to check harness terminal CPI. (Check the camshaft position sensor signal wave pattern.)
3. Connect the oscilloscope to check harness terminal SGT. (Check the crankshaft position sensor signal wave pattern.)
Standard Wave Pattern
Observation condition
FunctionSpecial pattern
Pattern heightLow
Pattern selectorDisplay
Engine conditionIdle

Wave Pattern Observation Points
  1. Check that cycle time becomes shorter when the engine speed increased.
 
 
 
Examples of Abnormal Wave Patterns
Example 1
  • Cause of problem
    • Sensor interface malfunction.
  • Wave pattern characteristics
    • Rectangular wave pattern is output even when the engine is not started.

Example 2
  • Cause of problem
    • Loose timing chain.
    • Abnormality in sensor disc.
  • Wave pattern characteristics
    • Wave pattern is displaced to the left or right.
 
 
 
 
INJECTOR
Required Special Tools:
  • MB991658: Test Harness
  • MB992110: Power Plant ECU Check Harness
 
 
Measurement Method
  1. Disconnect the injector connector, and connect the test harness special tool (MB991658) between the separated connector. (All terminals should be connected.)
  2. Connect the oscilloscope probe to injector connector terminal No. 2.

Alternate method
  1. Disconnect all ECM connectors. Connect the check harness special tool (MB992110) between the separated connectors.
  2. Connect the oscilloscope probe to each check harness connector terminal to analyze each cylinder:
    • Terminal INJ1 for the number 1 cylinder.
    • Terminal INJ2 for the number 2 cylinder.
    • Terminal INJ3 for the number 3 cylinder.
    • Terminal INJ4 for the number 4 cylinder.
Standard Wave Pattern
Observation conditions
FunctionSpecial pattern
Pattern heightVariable
Variable knobAdjust while viewing the wave pattern
Pattern selectorDisplay
Engine conditionIdle

Wave Pattern Observation Points
  • Point A: Height of injector coil induced voltage.
CONTRAST WITH STANDARD WAVE PATTERNPROBABLE CAUSE
Injector coil induced voltage is low or doesn't appear at allShort in the injector solenoid
Point B: Injector drive time
  1. The injector drive time should be synchronized with the scan tool tester display.
  2. When the engine is suddenly revved, the drive time will be greatly extended at first, but the drive time will soon return to original length.
 
 
 
 
IGNITION COIL AND IGNITION POWER TRANSISTOR
Required Special Tools:
  • MB991658: Test Harness
  • MB992110: Power Plant ECU Check Harness
 
 
Measurement Method
  1. Disconnect the ignition coil connector, and connect test harness special tool (MB991658) between the separated connector. (All terminals should be connected.)
  2. Connect the oscilloscope probe to ignition coil connector terminal No. 1.
 

 
 
Alternate method
  1. Disconnect all ECM connectors. Connect the check harness special tool (MB992110) between the separated connectors.
  2. Connect the oscilloscope probe to each check harness connector terminal to analyze each cylinder:
    • Terminal CIL1 for the number 1 cylinder.
    • Terminal CIL2 for the number 2 cylinder.
    • Terminal CIL3 for the number 3 cylinder.
    • Terminal CIL4 for the number 4 cylinder.
Standard Wave Pattern
Observation condition
FunctionSpecial pattern
Pattern heightLow
Pattern selectorDisplay
Engine conditionIdle

Wave Pattern Observation Points
  • Point: The power transistor control signal (ignition timing) is advanced when the engine speed is increased.
CONDITION OF WAVE PATTERN BUILD-UP SECTION AND MAXIMUM VOLTAGEPROBABLE CAUSE
Voltage value is too lowOpen-circuit in ignition primary circuit
 
 
 
Examples of Abnormal Wave Patterns
Example 1 (Wave pattern during engine cranking)
  • Cause of problem
    Open-circuit in ignition primary circuit
  • Wave pattern characteristics
    Voltage value is too low.