I would suggest getting the code read at Autozone or one of the similar auto parts stores first.
However, if you know what it is and just want to erase it, you can disconnect your negative battery terminal too. Once you do that just press on the brake pedal a few times and your brake lights will turn on, draining the leftover power in the system. Once your brake lights don't turn on anymore, then reconnect the battery cable and your ecu and cel will be reset.