Tom wraps up the GM ignition system discussion by walking through a real-world ICM failure on a Corsica 2.2, demonstrating how scope analysis can identify multiple simultaneous failure modes and confirm a successful repair.

The module also covers the evolution from the traditional EST-based system to GM's "up-integrated" system, where many ICM responsibilities are moved to the PCM, and how diagnostic strategy must adapt accordingly.

Key takeaways include:

• Using cursors and current measurements to catch failures that "look fine" at a glance
• Knowing which module owns which function so you know where to direct blame
• The three-legged stool approach: know the system, use action/reaction testing, follow a logical diagnostic trail
• Slowing down to fully analyze a capture before making additional hookups

The module closes with a preview of Toyota ignition systems, setting up the next presentation.