This module covers two case studies in ignition and driveability diagnosis, using waveform analysis and system logic to solve real-world misfires and stalling complaints.

The first case examines the Toyota 7M-GTE's unique distributorless ignition (DLI) system, including how the ECU uses IDGA/IDGB signals to route IGT to the correct coil. A burned wiring harness causing an intermittent IDGB fault is diagnosed through lab scope signal analysis.

The second case walks through a 93 Dodge Dakota 3.9 stumble/stall complaint, using tach output and crank sensor waveforms to identify cam signal instability caused by distributor drive bushing wear — a known TSB issue.

Key takeaways include:

• Approaching an unfamiliar system using first principles and signal logic
• Using signal relationships and binary combinations to identify coil firing sequences
• Recognizing how mechanical wear can produce confusing electronic symptoms
• Adapting scope strategy based on instrument limitations
• Verifying factory documentation, which can contain errors