HELP! I have an 1989 Corvette Convertible and I cannot seem to reset SERVICE ENGINE SOON light. I changed the alternator and battery today and BINGO! the light went OUT...BUT....an hour later it was back on> I ws told to disconnect the battery for 10 seconds and then re-attach to clear code. But to no avail it is abck on and really BUGGING ME! What do I do/try??