* Resetting the Check Engine Light (CEL): This doesn't actually reset the computer, but clears the diagnostic trouble codes (DTCs) stored in the computer's memory. The CEL will likely return if the underlying problem isn't fixed. This can often be done by disconnecting the negative (-) terminal of the battery for a few minutes (30 seconds to a couple of minutes is usually sufficient). Reconnecting the battery will often cause the computer to re-initialize, clearing the codes. Warning: Disconnecting the battery will erase radio presets and other personalized settings.
* Resetting the PCM (Powertrain Control Module): This is more involved and not something you typically do yourself. A full PCM reset requires specialized tools and software and is generally best left to a qualified mechanic. It's usually only done when other troubleshooting steps have failed.
* Resetting other modules (like the BCM - Body Control Module): Similar to the PCM, resetting these modules often requires specialized scan tools. They control various non-engine functions like power windows and locks, and resetting them might be necessary for certain issues, but it's usually not a DIY task.
* Clearing a specific fault: If you're experiencing a particular problem (e.g., intermittent ABS light), disconnecting the battery might not be enough. A diagnostic scan tool is often required to identify and clear specific error codes.
In short: For most situations, disconnecting the negative battery terminal for a few minutes is the closest thing to a "reset" that you can safely perform yourself on a 2002 Chevy Trailblazer. If you have a persistent problem, consult a mechanic or use an OBD-II scanner to diagnose the issue. Attempting more advanced resets without the proper knowledge and tools can potentially cause further problems.
