Park Avenue V6-3.8L SC VIN 1 (2005)
Body Control Module: Description and Operation
Body Control System
BODY CONTROL SYSTEM DESCRIPTION AND OPERATION
BCM FUNCTIONS
The body control module (BCM) performs multiple body control functions. The BCM can control devices directly connected to its outputs based on
input information. The BCM evaluates this information and controls certain body control systems by commanding outputs on or off. The BCM control
inputs can be:
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Sensors and switches that are directly connected to the BCM
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Class 2 serial data received from other control modules connected to the class 2 serial data link.
The BCM is also capable of controlling other vehicle systems that are not directly wired to the BCM. The BCM does this by sending specific
messages on the class 2 serial data link. The control module capable of performing the required function will respond to the BCM message.
The BCM functions include the following:
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Audible warnings-Refer to Audible Warnings Description and Operation in Instrument Panel, Gages and Console
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Automatic headlamp control-Refer to Exterior Lighting Systems Description and Operation in Lighting Systems
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Interior lighting-Refer to Interior Lighting Systems Description and Operation in Lighting Systems
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Heated seats-Refer to Heated Seats Description and Operation in Seats
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Retained accessory power (RAP)-Refer to Retained Accessory Power (RAP) Description and Operation
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Rear defogger-Refer to Rear Window Defogger Description and Operation in Heated Glass Element
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Shift lock control-Refer to Automatic Transmission Shift Lock Control Description and Operation in Shift Lock Control
POWER MODE
The BCM is the power mode master (PMM). Refer to Power Mode Description and Operation for more information.
ELECTRICAL LOAD MANAGEMENT
The power management function is designed to monitor the vehicle electrical load and determine when the battery is potentially in a high discharge
condition. This is accomplished by using a high accuracy battery voltage reading as an indicator of battery discharge rate. The following 6 levels of
load management will execute in the load management control algorithm when there is a high discharge condition:
1. The first action requests a vehicle idle speed increase to the powertrain control module (PCM) in order to raise alternator output.
2. The second action requests a greater vehicle idle speed increase to the PCM in order to raise alternator output.
3. The third action begins to shed vehicle loads in an attempt to remedy the heavy discharge condition.
4. The fourth action requests another vehicle idle speed increase to the PCM in order to raise further the alternator output.
5. The fifth action begins to shed further vehicle loads in an attempt to remedy the heavy discharge condition.
6. If the above five corrective actions fail, the sixth action of power management further sheds loads in a final attempt to remedy the high discharge
condition.
Loads subject to reduction include the following:
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The A/C clutch
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The heated mirrors
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The heated seats
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The rear defog
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The HVAC blowers
Each load management function, either idle boost or load-shed, is discrete. No two functions are implemented at the same time. During each load
management function, the PMM checks the battery temperature, battery voltage and amp-hour calculations and determines if the PMM should
implement a different power management function.
