Test A: Power Mode Mismatch: Notes
WARNING: This page is about a different car, the 2001 GMC Safari and 2001 Chevrolet Astro. However, it is still accessible from the selected car via links, so may be relevant.
NOTE:
On vehicles that have several control modules connected by serial data circuits, one module is identified as Power Mode Master (PMM). On this vehicle PMM is Body Control Module (BCM). PMM receives 3 signals/circuits from ignition switch. These are Unlock (IGN0), Run/Crank (IGN1) and Accessory (ACC) ignition switch signals/circuits.
NOTE:
Normal vehicle class 2 communications and module operations will not begin until system power mode has been identified. Ignition switch circuits are monitored by Power Mode Master (PMM) module in order to determine correct power mode. PMM communicates system power mode to all class 2 modules on class 2 serial data circuit. PMM functions are managed by Body Control Module (BCM).