Operation

OPERATION

The wait-to-start indicator gives an indication to the vehicle operator when the diesel engine glow plugs are energized in their pre-heat operating mode. This indicator is controlled by a transistor on the instrument cluster circuit board based upon cluster programming and electronic messages received by the cluster over the Controller Area Network (CAN) data bus from the Engine Control Module (ECM) (also known as the Powertrain Control Module/PCM).

The wait-to-start indicator Light Emitting Diode (LED) is completely controlled by the instrument cluster logic circuit, and that logic will only allow this indicator to operate when the instrument cluster detects that the ignition switch is in the ON position. Therefore, the LED will always be OFF when the ignition switch is in any position except ON. The LED only illuminates when it is provided a path to ground by the instrument cluster transistor. The instrument cluster will turn ON the wait-to-start indicator for the following reasons:

- Wait-To-Start Indicator Lamp-On Message - Each time the cluster receives an electronic wait-to-start indicator lamp-ON message from the ECM indicating that the diesel engine glow plugs are energized in their pre-heat operating mode, the wait-to-start indicator will be illuminated. The indicator remains illuminated until the cluster receives a wait-to-start lamp-OFF message indicating that the pre-heat mode of the glow plugs has been completed, until the ECM detects that the engine is running, or until the ignition switch is turned to the OFF position, whichever occurs first.

The ECM continually monitors the Electronic Ignition Switch/Central GateWay (EIS/CGW) and the engine coolant temperature sensor to determine when the glow plugs need to be energized in their pre-heat operating mode. The ECM then sends the proper lamp-ON and lamp-OFF messages to the ElectroMechanical Instrument Cluster (EMIC) (also known as the Cab Compartment Node/CCN or KOMBI). If the ECM sends a lamp-ON message to the EMIC after the engine has started, it may indicate that a malfunction has occurred and that the engine glow control system requires service. The ECM will store a Diagnostic Trouble Code (DTC) for any malfunction it detects.
For proper diagnosis of the engine glow control system and circuits, the engine coolant temperature sensor, the ECM, the EIS/CGW, the EMIC, the CAN data bus or the electronic communication related to wait-to-start indicator operation, a diagnostic scan tool is required. Refer to the appropriate diagnostic information.