Grand Voyager V6-3.8L VIN L (1999)
Body Control Module: Description and Operation
Part 1 of 3
INTRODUCTION
Six-Step Troubleshooting Procedure
Diagnosis of the body system is done in six basic steps:
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verification of complaint
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verification of any related symptoms
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symptom analysis
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problem isolation
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repair of isolated problem
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verification of proper operation
SYSTEM DESCRIPTION AND FUNCTIONAL OPERATION
AIRBAG SYSTEM
The airbag system is designed to provide increased driver and passenger protection if the vehicle is involved in a front end collision. The system is
most effective when used in conjunction with the seat belt system.
Both driver and passenger side airbag assemblies are now hybrid type which utilize a canister of compressed, inert gas to inflate the bag, instead
of sodium azide.
Currently, Chrysler Corporation uses two types of airbag control modules. The ASDM system is a mechanically-triggered system utilizing two
front impact sensors and a sensor inside the module. The AECM (AB, AS, JA and NS bodies only) is an electronically-triggered system that uses
only its own internal electronic sensor to trigger the airbags. This information will address the AECM type of module, the term "airbag control
module" (or ACM) will be used to refer to the module.
Functional Operation
Whenever the ignition key is turned to the "run" or "start" position, the airbag control module (ACM) performs a lamp check by turning the
AIRBAG warning lamp ON. The lamp stays lit for 6 to 8 seconds, then goes off. If the lamp remains OFF, it means that the ACM has checked the
system and found it to be free of discernible malfunctions. The airbag system is monitored by the ACM.
The ACM monitors critical input and output circuits within the airbag system, making sure they are operating correctly. Some circuits are tested
continuously; others are checked only under certain circumstances. The ACM provides diagnostic information about the airbag system to the
technician through the DRB via the CCD bus.
The deceleration or g-force resulting from the impact of a front-end collision causes the electronic sensor inside of the ACM to be triggered. This
causes the inflators to be actuated, thus deploying the airbags. The total time between determining to deploy and full inflation of the airbag is
approximately 40ms.
A new enhanced accident response feature has been added. This feature, upon deployment of the airbag, turns on the interior lights and unlocks the
power door locks (if equipped).
The AIRBAG warning lamp is the only point at which "symptoms" of a system malfunction can be observed by the customer.
Use the test procedures in this book to find the cause of any customer complaint regarding the AIRBAG warning lamp, such as:
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warning lamp does not come on at all
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warning lamp stays on
BODY CONTROL MODULE
The body control module (BCM) supplies vehicle occupants with visual and audible information and controls various vehicle functions. To
provide and receive information, the module is interfaced to the vehicle's serial bus communications network (the Chrysler Collision Detection
bus, or CCD bus). This network consists of the powertrain control module (PCM), the transmission control module (TCM), the electro/mechanical
instrument cluster (MIC), the airbag control module (ACM), the compass/mini- trip module and the controller antilock brake (CAB) module. The
BCM is operational when battery power is supplied to the module. Ignition switch power is needed for ignition switch functions.
The body control module provides the following features:
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automatic door locks
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battery protection
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CCD radio
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chimes
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compass/mini-trip support
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courtesy lamps
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BCM diagnostic support
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door lock inhibit
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headlamp time delay
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ignition key lamp
