Auto Electronics: chev avalanche, booster cables, sleep mode

Question
Ihave had no-start issues with my 2007 chev avalanche 5.3.
When I go to start it, the battery is completly dead and when we hook up booster cables the horn starts to blow until I hit the panic button on the remote.  This vehicle is equipped with factory auto-start and the problem occurs about once a month.

Answer
Hello Lina, If the Chevy has less than 36,000 miles on it, take it to the dealer for repair, it's still under warranty. A battery that goes dead after sitting a short period (less than a week) either needs replacing or has a parasitic drain on it. The battery needs to be properly charged and load tested first. Once confirmed good, a current drain test is next on the agenda. All late model vehicles are equipped with numerous electronic modules, each controlling a specific system and function. When the vehicle is shut down, these modules change from active mode to standby mode, then after a period of time, sleep mode. Once in sleep mode their power consumption is minimal, calling for a very small drain on the battery. More than likely, one or more of the modules on your Chevy, is not going into sleep mode and is consuming too much energy. The tough part is finding out which module is doing this and why! The diagnostic process involves connecting an ammeter to the battery cable and disconnecting individual circuits until the offender is found. At that point the cause will need to be determined. Any add on equipment should be disconnected first to aid in the diagnosis. Check for any doors, hood, or glove box left ajar and don't leave any electrical devices plugged into power outlets. This job needs to be performed by a seasoned pro using the right tools. That means someone with a GM specific scan tool and inductive ammeter. I wish you luck. Don.