Rendezvous FWD V6-3.5L VIN L (2006)
Body Control Module: Description and Operation
Power Mode
POWER MODE DESCRIPTION AND OPERATION
Power to many of this vehicle's circuits are controlled by the module that is designated the Power Mode Master (PMM). This vehicle's PMM is the Body
Control Module (BCM). The PMM controls which power mode (Run, Accessory, Crank, Retained Accessory Power, or Off) is active.
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 the
PMM is the body control module (BCM). The PMM receives 3 signals/circuits from the ignition switch. These are the Unlock (IGN 0), Run/Crank
(IGN 1) and Accessory (ACC) ignition switch signals/circuits.
To determine the correct power mode the PMM uses:
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The state of these signals/circuits, either switch closed (B+ = 1) or switch open (open = 0)
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The sequence of switch closures received by the PMM
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The status of the engine run flag
The chart indicates the modes detected and transmitted by the PMM.
Fail-Safe Operation
Since the operation of the vehicle systems depends on the power mode, there is a fail-safe plan in place should the power mode master (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
