Oscilloscope Patterns and Waveforms

IGNITION COIL AND [1][2]IGNITION POWER TRANSISTOR
- Ignition coil primary signal
- [1][2]Ignition power transistor control signal

MEASUREMENT METHOD
1. Disconnect the [1][2]ignition power transistor connector, and connect the special tool (test harness: MB991 348) in between. (All terminals should be connected.)
2. Connect the analyzer special patterns pickup to the [1][2]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 condition

Function Special patterns

Pattern height Low
Pattern selector Display
Engine RPM Approx. 1,200 RPM

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

Condition of wave pattern build-up Probable cause
section and maximum voltage

Rises from approx. 2V to Normal
approx. 4.5V at the top-right

2V rectangular wave Open-circuit in ignition primary circuit
Rectangular wave at power voltage. [1][2]Ignition power transistor malfunction

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 2V too low.





Example 2
Wave pattern during engine cranking

Cause of problem
Malfunction in [1][2]ignition power transistor

Wave pattern characteristics
Power voltage results when the [1][2]ignition power transistor is ON.