Oscilloscope Patterns and Waveforms
IGNITION COIL AND IGNITION POWER TRANSISTORRequired Special Tool:
MB991348: Test Harness Set
Measurement Method
1. Disconnect the connector, and connect test harness special tool (MB991348) in between. (All terminals should be connected.)
2. Connect the oscilloscope probe to each ignition power transistor connector terminal to analyze each cylinder:
- Terminal 1 for the number 3 and 6 cylinders
- Terminal 2 for the number 2 and 5 cylinders
- Terminal 3 for the number 1 and 4 cylinders
Alternate method (Test harness not available)
1. Connect the oscilloscope probe to PCM terminal 11.(When checking the number 1 and 4 cylinders.)
2. Connect the oscilloscope probe to PCM terminal 12.(When checking the number 3 and 6 cylinders.)
3. Connect the oscilloscope probe to PCM terminal 13.(When checking the number 2 and 5 cylinders.)
Standard Wave Pattern Part 1:
Standard Wave Pattern Part 2:
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 volts 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.