Serial Data Power Mode
WARNING: This page does not describe the selected car, but rather 6 other vehicles, including the 2004 Oldsmobile Bravada, 2004 GMC Envoy XUV, 2004 GMC Envoy XL, 2004 GMC Envoy, and 2004 Chevrolet TrailBlazer. 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 uses 3 signals from the ignition switch. These are the Ignition 0, Ignition 1, 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 | ||
|---|---|---|---|---|---|
| Accessory | Ignition 1 | Ignition 0 | |||
| OFF | Off-Awake or RAP | No | Inactive | Off | Off |
| UNLOCK | Unlock or RAP Unlock | No | Inactive | Off | On |
| ACC | Accessory | No | Active | Off | On |
| ON | Run | No | Active | On | On |
| START | Crank | No | Inactive | On | On |
| ON | Run | Yes | Active | On | On |