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 preheat operating mode. This indicator is controlled by a transistor on the IC electronic circuit board based upon programming and electronic messages received by the IC from the ECM over the CAN data bus.

The wait-to-start indicator is completely controlled by the IC logic circuit, and that logic will only allow this indicator to operate when the IC receives a battery current input on the fused ignition output (run-start) circuit. Therefore, the indicator will always be OFF when the ignition switch status is anything except ON or START. The icon only illuminates when it is provided a path to ground by the IC transistor. The IC will turn ON the wait-to-start indicator for the following reasons:

• Wait-To-Start Indicator Lamp-On Message  - Each time the IC 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 preheat mode, the wait-to-start indicator will be illuminated. The indicator remains illuminated until the IC receives a lamp-OFF message from the ECM, until the ECM detects that the engine is running, or until the ignition switch status transitions to OFF, whichever occurs first.

The ECM continually monitors the glow plug control circuits to determine when they are energized in their preheat operating mode. The ECM then sends the proper lamp-ON or lamp-OFF message to the IC. For proper diagnosis of the wait-to-start indicator, the ECM, the IC, 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.