Operation

OPERATION

The upshift indicator gives an indication to the vehicle operator that the engine speed is nearing its limit and a transmission upshift is necessary to prevent engine overspeeding. This indicator is controlled by the instrument cluster logic circuit based upon cluster programming and electronic messages received by the cluster from the Transmission Control Module (TCM) over the Controller Area Network (CAN) data bus.

The upshift 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 upshift indication will always be OFF when the ignition switch is in any position except ON or START. The instrument cluster will turn ON the upshift indicator for the following reasons:
- Upshift Indicator Lamp-On Message - Each time the cluster receives an electronic upshift indicator lamp-ON message from the TCM indicating that the engine speed is nearing its limit, the upshift indicator is illuminated. The indicator remains illuminated until the cluster receives a lamp-OFF message from the TCM, or until the ignition switch is turned to the OFF position, whichever occurs first.

The TCM continually monitors the engine speed and the Transmission Range Sensor (TRS) to determine the proper control outputs for the engine fuel, ignition and emissions systems. The TCM then sends the proper lamp-ON or lamp-OFF message to the ElectroMechanical Instrument Cluster (EMIC).

For proper diagnosis of the upshift indicator, the TCM, the EMIC, the CAN data bus or the electronic communication related to upshift indicator operation a diagnostic scan tool is required. Refer to the appropriate diagnostic information.