BCM Wake-Up/Sleep States

WARNING: This page is about a different car, the 2010 Pontiac G5 and 2010 Chevrolet Cobalt. However, it is still accessible from the selected car via links, so may be relevant.

The body control module (BCM) is able to control or perform all of the BCM functions in the wake-up state. The BCM enters the sleep state when active control or monitoring of system functions has stopped, and the BCM has become idle again. The BCM must detect certain wake-up inputs before entering the wake-up state. The BCM monitors for these inputs during the sleep state, where the BCM is able to detect switch transitions that cause the BCM to wake-up when activated or deactivated. Multiple switch inputs are needed in order to sense both the insertion of the ignition key and the power mode requested.

The BCM will enter a wake-up state, if any of the following wake-up inputs are detected:

Activity on the serial data line
Detection of a battery disconnect and reconnect condition
Headlamps are ON.
Ignition is turned ON.
Key-in-ignition switch
Park lamps are ON.
RFA message

The BCM will enter a sleep state when all of the following conditions exist:

The ignition switch is OFF.
No activity exists on the serial data line.
No outputs are commanded.
No delay timers are actively counting.
No wake-up inputs are present.

If all these conditions are met, the BCM will enter a low power or sleep condition. This condition indicates that the BCM, which is the power mode master (PMM) of the vehicle, has sent an OFF or OFF-ASLEEP message to the other systems on the serial data line.