The most important part of a vehicle's ignition system, including a GM vehicle, is the ignition control module because it regulates all aspects of the ignition, including the spark plugs. Mechanics use a special diagnostic scope to identify any existing problems within the ignition system, but if you do not have a scope, there are ways to visibly troubleshoot components of a GM vehicle's ignition system.
Grease or silicone should always be present on modules that are in good working condition to prevent the penetration of heat through the module's surface. Inspect the module for a visible layer of grease or silicone on the back of it. If this film is absent, the module needs to be replaced.
Install a timing light and monitor the engine for an irregular spark while the light is operating. If you notice an abnormal spark, but the spark plugs do not look damaged, the ignition module may be faulty.
Any cracks or damage to the module's surface indicate a problem. Remove the module and inspect it for damage or cracks on the surface or around the mounting screws. If there is any visible damage, replace the module.
