Oscilloscope Patterns and Waveforms

IGNITION COIL AND IGNITION POWER TRANSISTOR
- Ignition coil primary signal
- Ignition power transistor control signal

Measurement Method
1. Disconnect the distributor (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 distributor connector terminal 5.

Alternate method (Test harness not available)
1. Connect the analyzer special patterns pickup to ECM terminal 10.




Standard Wave Pattern Observation Conditions




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.