Oscilloscope Patterns and Waveforms

- 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 6.

ALTERNATE METHOD (TEST HARNESS NOT AVAILABLE)
1. Connect the analyzer special patterns pickup to ECM terminal 10.

STANDARD WAVE PATTERN (OBSERVATION CONDITIONS)
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 section and maximum Voltage
Probable cause

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

2V rectangular wave
Open-circuit in ignition primary circuit

Rectangular wave at power Voltage
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 ignition power transistor.

Wave Pattern Characteristics - Power Voltage results when the ignition power transistor is ON.