Serial Data Power Mode
WARNING: This page is about a different car, the 2002 Pontiac Aztek and 2002 Buick Rendezvous. 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 the power mode master (PMM). On this vehicle the PMM is the body control module (BCM). The PMM receives 3 signals/circuits from the ignition switch. These are the Unlock (IGNO), Run/Crank (IGN1) and Accessory (ACC) ignition switch signals/circuits.
To determine the correct power mode the PMM uses:
- The state of these signals/circuits, either switch closed (B+ = 1) or switch open (open = 0)
- The sequence of switch closures received by the PMM
- The status of the engine run flag
The chart below indicates the modes detected and transmitted by the PMM: