Serial Data Power Mode
WARNING: This page is about a different car, the 2004 Buick Regal and 2004 Buick Century. 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 BCM receives 4 signals/circuits from the ignition switch. These are the Ignition 0, Ignition 1, Crank and Accessory 1 ignition switch signals/circuits.
To determine the correct power mode the BCM 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 BCM
- The status of the engine run flag.
IMPORTANT:
Any ignition switch states not covered in this table indicates a DTC setting situation.
The chart indicates the modes detected and transmitted by the BCM:
Body Control System Description and Operation
| Power Mode Selected/Expected | Engine Run Flag Serial Data | Sampled Ignition Signal State | Power Mode State | |||
| Accessory | Ignition 0 | Ignition 1 | Crank | |||
| OFF-LOCK | 0 | 0 | 0 | 0 | 0 | OFF |
| Accessory | 0 | 1 | 0 | 0 | 0 | ACCESSORY |
| RAP | 0 | 1 to 0 | 0 | 0 | 0 | RAP |
| OFF-UNLOCK | 0 | 0 | 1 | 0 | 0 | UNLOCK |
| RAP | 0 | 1 to 0 | 1 | 0 | 0 | RAP-UNLOCK |
| Run | 0 | 1 | 1 | 1 | 0 | RUN |
| Crank | 0 | 0 | 1 | 1 | 1 | CRANK |
| Crank | 1 | 0 | 1 | 1 | 1 | CRANK |
| Run | 1 | 1 | 1 | 1 | 0 | RUN |