This vehicle is equipped with a Body Control Module (BCM) capable of performing various body control functions. The following is a list of operations and features the BCM controls:

The Power Mode Master (PMM) controls the power modes of other vehicle modules/systems. The PMM delivers either a class 2 command (Serial Data Power Mode), or a discrete power feed (Battery Guard) to control the power mode of the modules/systems throughout the vehicle.

The power mode signal may be as simple as a B+ input wired to a particular ignition switch contact. If this is also the B+ supply to the module/device, the module/device will only operate with the ignition contact closed to B+. An example of this is the starter relay when it is wired directly to the CRANK/START contact of the ignition switch. When the CRANK/START contacts are closed, the starter relay is energized and provides a current source to the starter and starter solenoid. When the ignition switch leaves the CRANK/START position, the switch contacts open and the starter relay is de-energized. This removes the current source from the starter and solenoid and the starter operation stops.

The modules using simple power mode are:

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 PMM receives two signals/circuits from the ignition switch. These are the 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:

To determine the correct power mode the PMM uses:

The chart below indicates the modes detected and transmitted by the PMM:

Battery Guard can control modules and systems that do not have Class 2 serial communications.

The Body Control Module (BCM) provides power regulation through the use of the battery guard relay to the following components:

The battery guard relay supplies the above components with power whenever the BCM is awake and for 15 minutes after the ignition transitions to the LOCK position.

Since the operation of the vehicle systems depends on the power mode, there is a fail-safe plan in place should the PMM fail to send a power mode message. The fail-safe plan covers those modules using exclusively serial data control of power mode as well as those modules with discrete ignition signal inputs.

Serial Data Messages

The modules that depend exclusively on serial data messages for power modes stay in the state dictated by the last valid PMM message until they can check for the engine run flag status on the serial data circuits. If the PMM fails, the modules monitor the serial data circuit for the engine run flag serial data. If the engine run flag serial data is True, indicating that the engine is running, the modules fail-safe to "RUN". In this state the modules and their subsystems can support all operator requirements. If the engine run flag serial data is False, indicating that the engine is not running, the modules fail-safe to "OFF-AWAKE". In this state the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.

Discrete Ignition Signals

Those modules that have discrete ignition signal inputs also remain in the state dictated by the last valid PMM message received on the serial data circuits. They then check the state of their discrete ignition input to determine the current valid state. If the discrete ignition input is active, B+, the modules will fail-safe to the "RUN" power mode. If the discrete ignition input is not active, open or 0 voltage, the modules will fail-safe to "OFF-AWAKE". In this state the modules are constantly checking for a change status message on the serial data circuits and can respond to both local inputs and serial data inputs from other modules on the vehicle.

The Retained Accessory Power (RAP) feature allows the use of the entertainment/phone system after the ignition is turned Off. The BCM controls this feature via the Class 2 serial data circuit.

The RAP feature is enabled when the ignition is in the ON position. It will not enable, however, with the door open and the ignition is turned to the LOCK position.

The RAP feature terminates when one of the following occurs: