Wait-To-Start Indicator

The wait-to-start indicator gives an indication to the vehicle operator when the diesel engine is too cool for efficient and reliable engine starting, and the 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 from the ECM over the CAN data bus.

The wait-to-start indicator LED 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 LED will always be OFF when the ignition switch is in any position except ON or START. 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 air temperature is too cool for efficient and reliable engine starting and the glow plugs are energized in their pre-heat mode, the wait-to-start indicator will be illuminated. The indicator remains illuminated until the cluster receives a lamp-OFF message from the ECM, 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 glow plug control circuits to determine when they are energized in their pre-heat operating mode. The ECM then sends the proper lamp-ON or lamp-OFF message to the CCN.