Oscilloscope Patterns and Waveforms

IGNITION COIL AND IGNITION POWER TRANSISTOR







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

Measurement Method
1. Disconnect the ignition coil connector, and connect the test harness special tool (MB991658) between the separated connector.
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. 143 for the number 2 cylinder.
- Terminal No. 150 for the number 3 cylinder.
- Terminal No. 148 for the number 4 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.