Oscilloscope Patterns and Waveforms

WAVE PATTERN INSPECTION USING AN ANALYZER
- Ignition coil primary signal
- Ignition power transistor control signal

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




2. Connect the analyzer special patterns pickup to ignition power transistor unit connector terminal No. 6.

Alternate Method (test Harness Not Available)
1. Connect the analyzer special patterns pickup to ECM terminal No. 10.




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 can not be seen, and voltage value is approximately 2V 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.