Operation

OPERATION

The low coolant indicator gives an indication to the vehicle operator that the level of coolant contained in the engine coolant reservoir is below the minimum recommended level. 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) (also known as the Engine Control Module/ECM) over the Controller Area Network (CAN) data bus.

The low coolant indicator function of the odometer Vacuum Fluorescent Display (VFD) 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 odometer VFD low coolant indication will always be OFF when the ignition switch is in any position except ON or START. The instrument cluster will turn ON the low coolant indicator for the following reasons:

- Low Coolant Indicator Lamp-On Message - Each time the cluster receives an electronic low coolant indicator lamp-ON message from the PCM indicating that the engine coolant level is low, the low coolant indicator will be illuminated. The indicator remains 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 PCM continually monitors an input from the coolant level sensor to determine the level of coolant in the engine coolant reservoir. The PCM then sends the proper lamp-ON or lamp-OFF message back to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN).

For proper diagnosis of the coolant level sensor, the PCM, the EMIC, the CAN data bus or the electronic communication related to low coolant indicator operation a diagnostic scan tool is required.