Temperature Warning Lamp/Indicator: Description and Operation

CIRCUIT OPERATION
The engine coolant temperature lamp is used to alert the operator that the coolant temperature has risen above the normal operating range When the Powertrain Control Module (PCM) determines a problem. a message is sent across the CCD Bus to the Body Control Module (BCM).

The PCM receives cool ant temperature information from the engine coolant temperature sensor. This sensor uses a variable resistor to send a signal to the PCM indicating engine coolant temperature.

The BCM processes this message and sends a signal on the CCD Bus to the instrument cluster for lamp illumination. This lamp also is illuminated for a few seconds, when the ignition switch is moved from the OFF to the RUN position as a bulb check.