Oscilloscope Patterns and Waveforms

IGNITION COIL AND IGNITION POWER TRANSISTOR







Required Special Tools:
- MB991658: Test Harness
- MB991923: Power Plant ECU Check Harness

Measurement Method
[Measure at the right bank (number 1, 3, 5 cylinders)]
1. Disconnect the intermediate connector B-32, and connect the test harness special tool (MB991658) between the separated connector.







2. Connect the oscilloscope probe to each intermediate connector B-32 terminal to analyze each cylinder:
- Terminal No. 2 for the number 1 cylinder.
- Terminal No. 7 for the number 3 cylinder.
- Terminal No. 3 for the number 5 cylinder.

[Measure at the left bank (number 2, 4, 6 cylinders)]
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. 3.

Alternate method







1. Disconnect all ECM [M/T] connectors or PCM [A/T] connectors. Connect the check harness special tool (MB991923) between the separated connectors.







2. Connect the oscilloscope probe to each check harness connector terminal to analyze each cylinder:
- Terminal No. 151 for the number 1 cylinder.
- Terminal No. 150 for the number 2 cylinder.
- Terminal No. 144 for the number 3 cylinder.
- Terminal No. 148 for the number 4 cylinder.
- Terminal No. 143 for the number 5 cylinder.
- Terminal No. 134 for the number 6 cylinder.










Wave Pattern Observation Points
Point: The power transistor control signal (ignition timing) is advanced when the engine speed is increased.







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.