How do you Reset the main computer in a car?

There is no single "main computer" in a car. Instead, there are multiple electronic control units (ECUs) that control different functions, such as the engine, transmission, air conditioning, etc.

Some manufacturers include a way to reset all or some of the ECUs by disconnecting the battery for a period of time (usually at least 10 minutes). However, this should only be done as a last resort, as it can also erase stored data, such as learned fuel trims, transmission shift points, etc.

If you're experiencing problems with your car, it's best to take it to a qualified repair shop for diagnosis and repair.