Engine Temperature

The engine temperature gauge gives an indication to the vehicle operator of the level of vehicle engine coolant temperature. This gauge is controlled by the Instrument Cluster (IC) (also known as the Instrument Panel Cluster/IPC) electronic circuit board based upon programming and electronic messages received from the Powertrain Control Module (PCM) (also known as the Engine Control Module/ECM) over the CAN data bus.

The engine coolant temperature gauge is an electronic bar graph within the IC electronic display unit that receives battery current on the IC electronic circuit board through a fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or START positions. The electronic display unit will not display this bar graph after the ignition switch is turned to the OFF position. The IC circuitry controls the bar graph display and provides the following features:

• Engine Temperature Message  - Following the ignition ON event, the bar graph is illuminated in a progressive fashion beginning at the bottom segment and working towards the top segment in a manner that is linear to the temperature indicated by the electronic engine temperature  message received by the IC from the PCM over the CAN data bus.
• Engine Temperature Low Message  - Once illuminated, the first segment of the engine temperature gauge bar graph will always remain illuminated while the ignition status remains ON and valid electronic engine temperature  messages are being received, even if the coolant temperature is -40° C (-40° F). The first segment of the gauge bar graph remains illuminated until the ignition switch is turned to the OFF position.
• Engine Temperature High or Critical Message  - Each time the IC receives an electronic engine temperature  message from the PCM over the CAN data bus indicating the temperature is high or critical, the appropriate gauge bar graph segments are illuminated by the IC. The Body Control Module (BCM) also receives the engine temperature  message from the PCM and sends an electronic message to the IC to illuminate the engine temperature indicator. The bar graph segments at the high end of the scale and the engine temperature indicator remain illuminated until the IC receives a message indicating that the temperature is below high or critical, or until the ignition switch is turned to the OFF position, whichever occurs first.

The PCM obtains the engine temperature data through a hard wired input from the engine coolant temperature sensor in the engine cooling system. The PCM continually monitors the engine coolant temperature sensor to determine the engine operating temperature. The PCM then sends the proper engine coolant temperature messages to the IC. If the IC turns on the engine temperature indicator due to a high engine temperature gauge reading, it may indicate that the engine or the engine cooling system requires service.

For proper diagnosis of the engine coolant temperature sensor, the PCM, the BCM, the IC, the CAN data bus or the electronic communication related to engine temperature gauge operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.