Engine Temperature Gauge

An engine coolant temperature gauge is standard equipment on all instrument clusters. The engine coolant temperature gauge is located in the upper right corner of the instrument cluster, to the right of the speedometer. The engine coolant temperature gauge consists of a movable gauge needle or pointer controlled by the instrument cluster circuitry and a fixed 45 degree scale on the cluster overlay that reads left-to-right from 120° C to 40° C for Canadian vehicles, or from 250° F to 110° F for United States vehicles. An International Control and Display Symbol icon for "Engine Coolant Temperature" is located on the cluster overlay, directly below the high end of the scale. Just to the right of the icon, the nomenclature "�C" or "�F" confirms the unit of measure for the gauge readings.

The engine coolant temperature gauge graphics are white against a black field, except for a single red graduation at the far left (high) end of the gauge scale, making them clearly visible within the instrument cluster in daylight. When illuminated from behind by the panel lamps dimmer controlled cluster illumination lighting with the exterior lamps turned On, the white graphics appear amber and the red graphics appear red. The orange gauge needle is internally illuminated. Gauge illumination is provided by Light Emitting Diode (LED) units soldered onto the instrument cluster electronic circuit board. The engine coolant temperature gauge is serviced as a unit with the instrument cluster.

The engine coolant temperature gauge gives an indication to the vehicle operator of the engine coolant temperature. This gauge is controlled by the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster from the Engine Control Module (ECM) over the Controller Area Network (CAN) data bus. The engine coolant temperature gauge is an air core magnetic unit that receives battery current on the instrument cluster electronic circuit board when the instrument cluster detects that the ignition switch is in the On position. The cluster is programmed to move the gauge needle back to the low end of the scale after the ignition switch is turned to the Off position. The instrument cluster circuitry controls the gauge needle position and provides the following features:
- Engine Temperature Normal Message - Each time the cluster receives a message from the ECM indicating the engine coolant temperature is within the normal operating range [up to about 120° C (250° F), the gauge needle is moved to the actual relative temperature position on the gauge scale.
- Engine Temperature High Message - Each time the cluster receives a message from the ECM indicating the engine coolant temperature is high [above about 120° C (250° F) the gauge needle is moved into the red warning zone on the gauge scale.

The ECM continually monitors the engine coolant temperature sensor to determine the engine operating temperature. The ECM then sends the proper engine coolant temperature messages to the instrument cluster. If the instrument cluster moves the engine coolant temperature gauge needle to red area of the gauge scale, it may indicate that the engine or the engine cooling system require service. For proper diagnosis of the engine coolant temperature sensor, the ECM, the CAN data bus, the electronic message inputs to the instrument cluster, or the instrument cluster circuitry that controls the engine coolant temperature gauge, a DRBIII(R) scan tool is required. Refer to the appropriate diagnostic information.