Engine Temperature

This gauge is controlled by the CCN circuit board based upon programming and electronic messages received from the Powertrain Control Module (PCM) over the CAN data bus.

The engine coolant temperature gauge is a stepper motor gauge that receives battery current on the CCN electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or START positions. The CCN 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 CCN circuitry controls the gauge needle position and provides the following features:

• Engine Temperature Message  - Each time the CCN receives an electronic engine temperature  message from the PCM indicating the temperature is between the low end of normal [about 41 °C (105 °F) for gasoline engines, or about 28 °C (82 °F) for diesel engines] and the high end of normal [about 124 °C (255 °F) for gasoline engines, or about 118 °C (244 °F) for diesel engines], the gauge needle is moved to the actual relative temperature position on the gauge scale.
• Engine Temperature Low Message  - Each time the CCN receives an electronic engine temperature  message from the PCM indicating the temperature is low [at or below about 40 °C (104 °F) for gasoline engines, or about 27 °C (81 °F) for diesel engines], the gauge needle is held below the graduation on the far left end of the gauge scale. The gauge needle remains below the low end of the gauge scale until the CCN receives a message from the PCM indicating that the temperature is above the low end of normal, or until the ignition switch is turned to the OFF position, whichever occurs first.
• Engine Temperature High or Critical Message  - Each time the CCN receives an electronic engine temperature  message from the PCM indicating the temperature is high [at or above about 127 °C (261 °F) for gasoline engines, or about 118 °C (244 °F) for diesel engines], the gauge needle is moved to the red graduation at the high end of the gauge scale, the engine temperature indicator is illuminated and a single chime tone is sounded. The gauge needle remains at the red graduation and the engine temperature indicator remains illuminated until the CCN receives a message from the PCM indicating that the temperature is below about 124 °C (255 °F) for gasoline engines, or about 115 °C (239 °F) for diesel engines, or until the ignition switch is turned to the OFF position, whichever occurs first. The chime tone feature will only repeat during the same ignition cycle if the engine temperature indicator is cycled OFF and then ON again by the appropriate messages from the PCM.
• Communication Error  - If the CCN fails to receive an engine temperature  message, it will hold the gauge needle at the last indication for about five seconds or until the ignition switch is turned to the OFF position, whichever occurs first. After five seconds, the CCN will move the gauge needle to the low end of the gauge scale.

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 CCN. For further diagnosis of the engine coolant temperature gauge or the CCN circuitry that controls the gauge. Refer to DIAGNOSIS AND TESTING . If the CCN 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. The engine coolant temperature gauge is serviced as a unit with the instrument cluster.