I had a battery CEL light come on yesterday. I took the battery to have it tested and it failed to hold a charge. Since it was only 16 months old it was replaced by the store where I purchased it free. Anyway, I put the new battery in the truck and the CEL is still on. Is there something in the GMC that requires codes to be reset by computer to get the CEL to clear? If the problem that caused the CEL in the first place was the bad battery, should the warning light have gone out once the new battery was installed? Ideas. . . Thanks, Dave in WA State