Grand Cherokee 2WD L6-4.0L VIN S (1997)
Check Gauges Lamp: Description and Operation
SYSTEM OPERATION
The check gauges lamp gives an indication when certain gauges reflect a condition requiring immediate attention. The lamp is turned on by the
instrument cluster circuitry for about three seconds after the ignition switch is turned to the On position as a bulb test. After the bulb test, the lamp
is controlled by the instrument cluster circuitry based upon a message received from either the Body Control Module (BCM) or the Powertrain
Control Module (PCM) on the Chrysler Collision Detection (CCD) data bus.
The BCM and PCM use several inputs to decide whether a condition exists requiring the check gauges lamp to be turned on. The responsible
module then sends the proper message to the instrument cluster on the CCD data bus to turn the lamp on or off. When the instrument cluster
circuitry receives a check gauges lamp-on message, it sends a chime request message to the BCM on the CCD data bus for a chime tone to sound.
The conditions monitored and the responsible modules are:
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Engine coolant temperature is high or critical (BCM)
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Engine oil pressure is low (BCM)
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Charging system failure (PCM)
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System voltage is high (PCM).