Oscilloscope Patterns and Waveforms

IGNITION COIL AND IGNITION POWER TRANSISTOR
- Ignition coil primary signal
Refer to Ignition System.
- 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 the ignition power transistor connector terminal 2 (No.2 - No. 3) and terminal 7 (No.1 - No.4) respectively.

Alternate method (Test harness not available)
1. Connect the analyzer special patterns pickup to ECM terminal 10 and connection terminal 23 respectively.

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 cannot be seen and voltage value is approximately 2 V 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.