Serial Data Power Mode
WARNING: This page is about a different car, the 2002 GMC Sierra, 2002 GMC Cab & Chassis Sierra, 2002 Chevrolet Silverado, and 2002 Chevrolet Cab & Chassis Silverado. 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 (PMN). 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 = O)
- The status of the engine run flag.
The chart indicates the modes detected and transmitted by the BCM. See Fig 1.