Serial Data Power Mode
WARNING: This page is about a different car, the 2003 Chevrolet SSR. 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 BCM. The BCM uses 3 signals from the ignition switch. These are the Ignition 0 (Unlock), Ignition 1 (Run/Crank), and Accessory.
To determine the correct power mode the BCM uses:
- The state of these signals
- The sequence of switch closures received by the BCM
- The status of the engine run flag
The chart indicates the power modes detected and transmitted by the BCM:
Correct Ignition Switch Inputs
| Ignition Key Position | Power Mode Parameter | Engine Running | Sampled Ignition Signal State | ||
|---|---|---|---|---|---|
| Ignition Accessory | Ignition 1 (Run/Crank) | Ignition 0 (Unlock) | |||
| OFF | Off-Awake or RAP | No | Inactive | Inactive | Inactive |
| UNLOCK | Unlock or RAP Unlock | No | Inactive | Inactive | Active |
| ACC | Accessory | No | Active | Inactive | Active |
| ON | Run | No | Active | Active | Active |
| START | Crank | No | Inactive | Active | Active |
| ON | Run | Yes | Active | Active | Active |