Coolant Level Indicator Lamp: Description and Operation
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 Indicator Lamp-On Message - Each time the cluster receives an electronic coolant low indicator 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 textual warning
and icon are cycled OFF and then ON again by the appropriate 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 lamp-ON or lamp-OFF message to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN). If
the instrument cluster turns ON the coolant low indicator and icon due to a low coolant level, it may indicate that the engine or the engine cooling system
For proper diagnosis of the engine coolant level switch, the PCM, the EMIC, the CAN data bus or the electronic communication related to coolant low
indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.