My new battery I bought for 2003 Avalanche is dead in the mo rning. Something is on 2003 Chevrolet Avalanche 1500

pulling down the power to my battery at night. Were do I start troubleshooting. The alternator seems to be O.K.

Asked by for the 2003 Chevrolet Avalanche 1500
This is a common problem. One of the computer modules is not going to sleep. Not knowing your level of knowledge it will take an experienced tech to find out which module is causing the problem. Probably the BCM (Body Control Module).