Ignition Control Module: Testing and Inspection

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IGNITION COIL AND IGNITION POWER TRANSISTOR

Required Special Tool:
MB991348: Test Harness Set

Measurement Method
1. Disconnect the ignition coil connector, and connect test harness special tool, MB991348, in between. (All terminals should be connected.)




2. Connect the oscilloscope probe to ignition coil connector terminal No. 3.

Alternate method (Test harness not available)


1. Connect the oscilloscope probe to the ECM terminal No. 10 (for number 1 - number 4), terminal No. 23 (for number 2 - number 3).


1. Connect the oscilloscope probe to the PCM terminal No. 11 (for number 1 - number 4), terminal No. 12 (for number 2 - number 3).







Standard Wave Pattern




Wave Pattern Observation Points

Point: Condition of wave pattern build-up section and maximum voltage (Refer to abnormal wave pattern examples 1 and 2.

Examples of Abnormal Wave Patterns




Example 1 (Wave pattern during engine cranking)

Cause of problem
- Open-circuit in ignition primary circuit

Wave pattern characteristics
- Top-right part of the build-up section cannot be seen, and voltage value is approximately 2 volts too low.




Example 2 (Wave pattern during engine cranking)

Cause of problem
- Malfunction in ignition power transistor

Wave pattern characteristics
- Power voltage results when the ignition power transistor is ON.
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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.