Commander 4WD V8-4.7L VIN N (2006)
Check Gauges Lamp: Description and Operation
CHECK GAUGES INDICATOR
DESCRIPTION
A check gauges indicator is standard equipment on all instrument clusters. The check gauges indication appears within the reconfigurable dot matrix
Organic Light Emitting Diode (OLED) display unit. The check gauges indicator consists of a textual CHECK GAUGES message which appears in place
of the compass/trip computer information in the dot matrix display.
The dot matrix OLED is soldered onto the cluster electronic circuit board, and is visible through a window with a smoked clear lens located on the lower
edge of the tachometer gauge dial face of the cluster overlay. The dark lens over the OLED prevents it from being clearly visible when it is not
illuminated. The check gauges textual message appears in the same blue-green color and at the same lighting level as the compass/trip computer
information when it is illuminated by the instrument cluster electronic circuit board.
The check gauges indicator is serviced as a unit with the OLED in the instrument cluster.
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 a message from the PCM indicating the engine coolant
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 engine temperature is below about 124° C (255° F), 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 engine 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
engine coolant temperature messages to the instrument cluster. 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 CAN data bus, or the electronic message inputs to the instrument cluster that control the check gauges
indicator, a diagnostic scan tool is required.
