Serial Data Power Mode
WARNING: This page is about a different car, the 2002 Chevrolet Monte Carlo, 2002 Chevrolet Impala, 2001 Chevrolet Monte Carlo, and 2001 Chevrolet Impala. However, it is still accessible from the selected car via links, so may be relevant.
On vehicles that have several control modules connected by serial data circuits, one module is Power Mode Master (PMM). On this vehicle PMM is Body Control Module (BCM). BCM receives 3 signals/circuits from ignition switch: ACC/RUN/CRANK (ignition 0), RUN/CRANK (ignition 1) and ACC/RUN (accessory).
To determine correct power mode, BCM uses following information:
- State of these signals/circuits, either switch closed (battery voltage = 1) or switch open (open = 0).
- Sequence of switch closures received by BCM.
- Status of engine run flag.