Commander 4WD V8-4.7L VIN N (2006)
Coolant Level Indicator Lamp: Description and Operation
COOLANT LOW INDICATOR
A coolant low indicator is standard equipment on all instrument clusters. However, on vehicles not equipped with an optional diesel engine this indicator
is electronically disabled. The coolant low indication appears within the reconfigurable dot matrix Organic Light Emitting Diode (OLED) display unit.
The coolant low indicator consists of a textual COOLANT LOW message and icon 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 coolant low textual message and icon appear in the same blue-green color and at the same lighting level as the compass/trip computer
information when they are illuminated by the instrument cluster electronic circuit board.
The coolant low indicator is serviced as a unit with the OLED in the instrument cluster.
The coolant low indicator gives an indication to the vehicle operator when the diesel engine coolant level is low. 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 coolant low 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 coolant low indication will always be off when the ignition switch is in any position
except ON or START. The instrument cluster will turn on the coolant low indicator for the following reasons:
Coolant Low Lamp-On Message - Each time the cluster receives a coolant low lamp-on message from the PCM indicating the engine coolant
level is low the coolant low textual warning and icon are illuminated, and a single chime tone is sounded. The coolant low textual warning and
icon remain illuminated until the cluster receives a lamp-off message from the PCM, 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 coolant low textual warning and icon are
cycled off and then on again by the appropriate coolant low lamp-on and lamp-off messages from the PCM.
The PCM continually monitors the engine coolant level switch on the coolant bottle to determine the level of the engine coolant. The PCM then sends
the proper coolant low lamp-on and lamp-off messages to the instrument cluster. If the instrument cluster turns on the coolant low indicator and icon due
to a coolant level, it may indicate that the engine or the engine cooling system requires service. For proper diagnosis of the engine coolant level switch,
the PCM, the CAN data bus and the electronic message inputs to the instrument cluster that control the coolant low indicator, a diagnostic scan tool is