Serial Data Power Mode

On vehicles that have several control modules connected by serial data circuits, one module is the Power Mode Master (PMM). On this vehicle PMM is the Body Control Module (BCM). PMM receives 2 signals/circuits from ignition switch. These are Run/Crank (IGN1) and Accessory (ACC) ignition switch signals/circuits. Retained Accessory Power (RAP) is an example of serial data power mode. Modules using serial data power mode are:

• Radio.
• Radio Integration Module (RIM).
• Dealer installed cellular phone.

To determine correct power mode the PMM uses:

• State of these signals/circuits, either switch closed (battery voltage = 1) or switch open (open = 0).
• Sequence of switch closures received by PMM.
• Status of engine run flag.