Oscilloscope Check
IGNITION COIL AND IGNITION POWER TRANSISTORRequired Special Tool:
- MB991348: Test Harness Set
Measurement Method
1. Disconnect the con nector1 and connect test harness special tool, (MB991348), in between. (All terminals should be connected.)
2. Connect the oscilloscope probe to ignition coil connector terminal 3.
Alternate method (Test harness not available)
1. Connect the oscilloscope probe to ECM
Standard Wave Pattern
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 can not 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.