What needs to happen is to perform a Parasitic Draw Test on the Electrical System. Your Dealer should have a competent Technician to perform this.
I suspect you have one of the 17 modules "Waking Up" inadvertantly after the vehicle is shut off. The BCM, or Retained Accessory Power Module have been culprits in my service bay through the later years, but that would be for the Tech to verify.
If the vehicle is still under warranty, I would also give GM Customer Service a ring & let them know what is happening. I would also let the Service Manager know that you expect Factory Technical Assistance being involved, & what notes they have taken on your vehicle.
These situations can be quite trying for the Tech, & your patience is much appreciated, I'm sure, but your vehicle should be able to be fixed!
Also check your local "Lemon Laws" for anything that may help you if the dealer can't or won't.
Before I let you go, here's a bulletin I found on just this situation. I would present it to your dealer as well, or just copy the bulletin number down & present it to them, I'm sure they'll be able to find it!
|Electrical - Battery Goes Dead Overnight |
Bulletin No.: 06-06-03-009
Date: October 19, 2006
Diagnostic Information on Battery Draw No Start - Body Control Module
, BCM Power Timer Models:
2006-2007 Buick Lucerne
2006-2007 Cadillac DTS
2006-2007 Chevrolet Impala, Monte Carlo
2007 Cadillac Escalade, Escalade ESV
, Escalade EXT
2007 Chevrolet Avalanche, Equinox, Tahoe, Silverado, Suburban
2007 GMC Sierra, Yukon, Yukon XL, Denali, Denali XL
2007 Pontiac Torrent
When performing normal diagnosis on a battery that has gone dead overnight, a technician may notice that the vehicle has approximately 4.1 amp draw on the system. The draw may be steady or may drop down to a low milliamp reading for 1-2 seconds and then rise back up to the 4.1 amp range. If this amp draw condition is observed, check for aftermarket accessories or an improperly installed GM accessory that is wired into circuit 6815 (orange wire) for courtesy lamps. Anytime aftermarket accessories are installed into the courtesy lamp circuit, it can cause the inadvertent power timer in the body control module (BCM) to keep resetting. The BCM will remain awake and cause the draw of approximately 4.1 amps.
When servicing a vehicle with this concern, back out pin 1 of the connector 2 at the BCM and see if the draw goes away. If the draw goes away, check for an aftermarket accessory (Lojack, non-factory DVD system, alarm, etc.) that is improperly installed in circuit 6815.