* Reset the radio: If you're locked out of the radio, you'll need the radio's security code. This isn't a computer reset, but a radio-specific unlock. Your owner's manual should have instructions, or you might find the code on a sticker somewhere in the vehicle (often in the glove compartment or under the radio).
* Reset the PCM (Powertrain Control Module): This is a more involved process and is usually done to address specific problems like a check engine light or erratic performance. It *doesn't* involve a button press; it typically requires disconnecting the battery's negative terminal for a certain amount of time (often 30 minutes to an hour), which resets the PCM to factory settings. Caution: This will erase any learned driving parameters, and the car's computer will need to relearn your driving style. It may also cause the loss of some radio presets.
* Reset a specific system: Are you having issues with a particular feature (like the seat memory or climate control)? The owner's manual will often specify how to reset individual systems.
* "Reset" a stuck system: If you have a system that's frozen or unresponsive (highly unlikely in a 2002 DeVille), you might need to try disconnecting the battery as mentioned above. However, this is a last resort.
To clarify what you need, please describe the problem you're trying to solve. Knowing the specific issue will help determine the correct action. For example, "My check engine light is on" is very different from "My radio is asking for a code."
