Serial Data Power Mode
WARNING: This page does not describe the selected car, but rather 7 other vehicles, including the 2002 GMC Yukon XL, 2002 GMC Yukon, 2002 Chevrolet Tahoe, 2002 Chevrolet Suburban, and 2002 Chevrolet Avalanche. 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 2 signals/circuits from the ignition switch. These are the Ignition 1 and Ignition 3 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 status of the engine run flag.
The chart indicates the modes detected and transmitted by the BCM:
Correct Ignition Switch Inputs
| Ignition Key Position | Power Mode Parameter | Engine Run Flag Serial Data | Sampled Ignition Signal State | |
|---|---|---|---|---|
| Ignition 1 | Ignition 3 | |||
| Off | Off-Awake | 0 | 0 | 0 |
| Unlock | Off-Awake | 0 | 0 | 0 |
| Run | Run | 0 | 1 | 1 |
| Crank | Crank | 0 | 1 | 0 |
| Accessory | Off-Awake | 0 | 0 | 0 |
| Run | Run | 1 | 1 | 1 |