Cherokee 4WD L6-4.0L VIN S (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 on the CCD data bus.
If the PCM message indicates that coolant temperature is high, the instrument cluster circuitry moves the gauge needle into the beginning of the
red zone on the gauge face, turns on the Check Gauges lamp, and generates a single chime tone. If the PCM message indicates that coolant
temperature is critical, the instrument cluster circuitry moves the gauge needle to the stop at the end of the red zone on the gauge face.
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. Refer to Powertrain Management/Computer and Control Systems
for more information on the PCM and the coolant temperature sensor.
