Safety Warning

DIY auto repair can cause serious injury, fire, or vehicle damage. These guides are for informational purposes only. Always follow OEM torque specs, wear PPE, and consult a certified mechanic if you are unsure. You are solely responsible for your safety.

Ignition Control Module: Testing and Inspection

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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. 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 No. 4 for the number 1 cylinder.
- Terminal No. 5 for the number 2 cylinder.
- Terminal No. 20 for the number 3 cylinder.
- Terminal No. 21 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.

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

• You smell fuel, burning insulation, or see smoke.
• Brakes feel soft, pull hard to one side, or make grinding noises.
• The engine overheats, stalls repeatedly, or misfires under load.
• You are missing required tools, torque specs, or safe lifting equipment.
• You are not confident in the next step or safety outcome.