Oscilloscope Patterns and Waveforms

Ignition Power Transistor Control Signal

Measurement Method
1. Disconnect the ignition coil 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 coil connector terminal 3.
Alternate method (Test harness not available)
1. Connect the analyzer special patterns pickup to ECM terminal 10(No.1 - No.4), terminal 23 (No.2 - No.3) respectively.





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 cannot be seen and voltage value is too low, approximately 2V.





- 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.