Prowler V6-3.5L VIN G (1999)
Body Control Module: Description and Operation
Part 2 of 3
EXTERIOR LIGHTING CONTROL
The head lamps and park lamps are controlled by external relays which are controlled by the body control module. The headlamp relays are
located in the power distribution center and the parklamp relay is located in the micro relay center behind the glove box. When the park lamp
switch is turned ON (signals as a ground) the BCM then grounds the park lamp relay to provide power to the park, tail and marker lamps. The park
lamp power feed, which is controlled by the BCM, also provides back-up power to the BCM. In the event that the ignition is turned off with the
park lamps still on, the BCM will function normally (as if the IOD had been reconnected) until the park lamps are turned off. When the headlamp
switch is turned on, (signals as a B+ feed) the BCM grounds low beam and high beam headlamp relay coils to turn on the headlamps. However,
the high beams will not turn on until the dimmer switch is activated.
Headlamp Time Delay
The headlamp delay feature keeps the headlamps on for 60 seconds, giving the driver and passenger security when exiting the vehicle. It is
activated by sequentially turning off the ignition, and then turning off the headlamps. The headlamps must be turned oft within 45 seconds of
the ignition transition to off, to activate the headlamp delay. Once the headlamp delay has started the headlamps will remain on for 60 seconds
or until the park lamps (or headlamps) are cycled on/off or the ignition is turned on.
Battery Protection
If the park lamp or headlamp switch remains on for more than 3 minutes while the ignition is oft, the headlamps and park lamps will be turned
off by the BCM and the input causing the lamps to be on will be ignored until the condition is corrected. Once the 3 minute timeout has
elapsed the BCM will enter sleep mode. This feature provides protection to avoid running the battery down in the event the customer fails to
turn the lamps off.
If the park lamp or headlamp switch remains on for more than 3 minutes while the ignition is off, the headlamps and park lamps will be turned
oft by the BCM and the input causing the lamps to be on will be ignored until the condition is corrected. Once the 3 minute timeout has
elapsed the BCM will enter sleep mode. This feature provides protection to avoid running the battery down in the event the customer fails to
turn the lamps off.
INSTRUMENT CLUSTER (MIC)
The Prowler utilizes a 'smart' cluster similar to the cluster on Cirrus/Stratus/Breeze and Sebring convertible. The differences are the addition of an
oil pressure and voltmeter gauge internal to the cluster and a new external tachometer that is mounted to the top of the steering column. There is
also a new Liquid Crystal Display (LCD) odometer. This odometer is more easily read in direct sunlight. The tachometer and the voltmeter gauges
are hardwired and are not part of the self test routine. They cannot be actuated. As mentioned previously, the tach is hardwired directly to the
PCM, the illumination circuit, however, is part of the instrument panel lighting circuit. The voltmeter is hardwired to the B (+) circuit through the
ignition switch.
As in other vehicles, the cluster positions its gauges based on a message formulated by the BCM for gauge position. All the sensors that are
responsible for a gauge message are hardwired to the BCM. The BCM then builds the message and sends it over the CCD bus where the cluster
will receive the message, decode it, and position all the gauge pointers at their proper positions.
The cluster also contains hardwired and CCD bus controlled warning lamps. A hardwired lamp is usually supplied B (+) by the cluster and ground
by the circuit that it monitors. Any circuit that has a lamp that is CCD bus controlled will be an input to the BCM, except the Airbag Lamp which
receives it's CCD messages from the Airbag Control Module (ACM). If no messages are received from the ACM for 5 seconds the Airbag lamp
will be turned on.
There is an on-board self-test that can be actuated stand-alone or with the DRB. During the self-test, the cluster will position all the gauges at
predetermined calibration points, the CCD controlled lamps will be illuminated, as well as the segments of the LCD odometer. This allows
verification of gauge operation, CCD operation, as well as a visual check of all the individual segments in the LCD odometer.
INTERIOR LIGHTING
COURTESY LAMP CONTROL
The interior courtesy lamps located in the right and left foot well area, the rear view mirror and the ignition switch halo lamp are hardwired
together and are controlled by the BCM. They can be activated by the dome lamp switch, opening a door or if the RKE activates the BCM 30
second illuminated entry timer. The interior lamps will then fade to off over a 5 second period.
Reading Lamps
The reading lamps and control switches are mounted on the rear view mirror.
Interior Lamp Battery Protect Feature (Load Shedding)
To protect the battery from excessive current draw, the courtesy, halo, reading and glove box lamps are shut oft after 15 minutes if they have
been left ON or a door has been left ajar after the ignition key is removed from the ignition. This is accomplished by the BCM which removes
ground from these lamps.
INSTRUMENT PANEL DIMMING
I/P dimming is accomplished using the body computer. The panel dimming level switch is read by the body computer and converted to a value that
