Grand Caravan AWD V6-201 3.3L (1992)
Body Control Module: Description and Operation
Body Control Module
There are two body controllers available on the 1992 AS body, depending on the cluster type (electronic instrument cluster or electro/mechanical
instrument cluster).
The body controller provides power or ground for a variety of systems. It uses a voltage drop to monitor these systems.
The body controller is the only module that has the capability of providing both bias and termination on the CCD bus system.
The body controller is used to store odometer information displayed in the electronic instrument cluster (see descriptions later in this section).
CCD Bus
The Chrysler Collision Detection multiplex system (CCD bus) consists of a twisted pair of wires. These wires run from one module to another. They
receive and deliver coded information between the modules. The information is coded to identify the message as well as the importance of the message.
When there are multiple messages trying to access the CCD bus at one time, the code is used to determine which one has higher priority and is allowed to
access the bus first.
The two wires (D1) and (D2) of the twisted pair that makes up the CCD multiplex system are called "bus+" (bus plus) and "bus-" (bus minus). Both
wires have a measurable voltage level of roughly 2.5 volts. In order to maintain the 2.5 volts on each line and provide a means of transportation for the
coded messages, there is a "voltage divider network." This network consists of some modules with bias and some with termination. Bias is the part of the
voltage divider network that places both bus+ and bus- at 2.5 volts. Termination is the circuitry required to complete the voltage divider network and
also provide some electromagnetic protection for the bus.
NOTE: Communication over the bus is essential to the proper operation of the vehicle's on-board diagnostic systems and the DRBII. Problems with the
operation of the bus or DRBII must be corrected before proceeding with diagnostic testing. If there is a problem, refer to Information Bus for diagnosis
and repair procedures.
Compass Mini-Trip Computer (CMTC)
The Compass/Mini-Trip module is located in the overhead console. It displays to the driver the direction the vehicle is traveling and the current outside
temperature, as well as the following Traveler navigational information: average fuel economy, distance to empty (DTE), elapsed time (ET) and trip
odometer (ODO). The information needed for the Traveler functions is received over the CCD bus from the body controller.
If the Compass Mini-Trip module has been replaced, it may be necessary to reset the calibration following the steps below.
TO SET THE COMPASS:
The Compass/Mini-Trip module is self-calibrated and requires no adjustment. The word CAL will be displayed to indicate that the compass is in
the fast calibrating mode. CAL will turn off after the vehicle has gone in three complete circles without stopping, in an area free of magnetic
disturbance.
If the module displays the temperature while the compass is blank, the vehicle must be demagnetized.
If the compass still goes blank after the vehicle is demagnetized, the Compass/Mini-Trip module must be replaced.