Grand Cherokee 4WD V8-5.2L VIN Y (1998)
Temperature Gauge: Description and Operation
SYSTEM OPERATION
The coolant temperature gauge gives an indication of the engine coolant temperature. The instrument cluster circuitry controls the gauge pointer
position. The instrument cluster circuitry calculates the proper gauge pointer position based upon an engine coolant temperature message received
from the Powertrain Control Module (PCM) on the Chrysler Collision Detection (CCD) data bus.
The PCM uses an input from the engine coolant temperature sensor and internal programming to decide what engine coolant temperature message
is required. The PCM then sends the proper message to the instrument cluster and the Body Control Module (BCM) on the CCD data bus.
The BCM also monitors the PCM engine coolant temperature messages. If the PCM message indicates that coolant temperature is high or critical,
the BCM sends a message to the instrument cluster to turn on the Check Gauges lamp and to move the coolant temperature gauge needle to the
corresponding high or critical position of the gauge scale.
The engine coolant temperature sensor is installed in a threaded hole that penetrates a coolant passage of the engine. It is a thermistor-type sensor
that changes its internal resistance with changes in engine coolant temperature.
