Serial Data Power Mode
WARNING: This page is about a different car, the 2003 Pontiac Grand Am and 2003 Oldsmobile Alero. 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 PMM receives 3 discreet ignition switch signals to differentiate which power mode will be sent over the Class 2 Serial Data circuit.
To determine the correct power mode the PMM uses the following circuits:
- Ignition 0
- Ignition 1 voltage
- Ignition 3 voltage