Check Gauges Indicator - Operation

OPERATION

The check gauges indicator gives an indication to the vehicle operator when the engine coolant temperature gauge indicates the coolant temperature is high or critical. This indicator is controlled by the instrument cluster logic circuit based upon cluster programming and electronic messages received over the Controller Area Network (CAN) data bus from the Powertrain Control Module (PCM).

The check gauges indicator function of the reconfigurable dot matrix Organic Light Emitting Diode (OLED) display unit is completely controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster receives a battery current input on the fused ignition switch output (run-start) circuit. Therefore, the OLED check gauges indication will always be OFF when the ignition switch is in any position except ON or START. The instrument cluster will turn ON the check gauges indicator for the following reasons:

- Engine Temperature High or Critical Message - Each time the cluster receives an electronic engine coolant temperature message from the PCM indicating the temperature is high [at or above about 127° C (261° F) for gasoline engines, or about 128° C (262° F) for diesel engines], or critical [above about 132° C (270° F)] the engine coolant temperatures gauge needle is moved to the appropriate position at the high end of the gauge scale, the check gauges textual warning is displayed, and a single chime tone is sounded. The check gauges textual warning remains illuminated until the cluster receives a message from the PCM indicating that the temperature is below about 124° C (255° F), until the cluster arbitrator logic determines that another display request has priority, 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 check gauges textual warning is cycled OFF and then ON again by the appropriate temperature messages from the PCM.

The PCM continually monitors the engine coolant temperature sensor to determine the engine operating temperature. The PCM then sends the proper messages to the instrument cluster, also known as the Cab Compartment Node (CCN). If the instrument cluster turns on the check gauges indicator due to a high or critical 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 CCN, the CAN data bus or the electronic communication related to check gauges indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.