Upshift Indicator - M/T: Description and Operation

An upshift indicator is standard equipment on all instrument clusters. However, on vehicles not equipped with a manual transmission, this indicator is disabled. The upshift indicator is located near the center of the tachometer gauge in the instrument cluster overlay, to the left of center. The upshift indicator consists of an upward pointed arrow icon that is a stenciled cutout in the opaque layer of the instrument cluster overlay. The dark outer layer of the overlay prevents the indicator from being clearly visible when it is not illuminated. An amber lens behind the cutout in the opaque layer of the overlay causes the icon to appear in amber through the translucent outer layer of the overlay when the indicator is illuminated from behind by a Light Emitting Diode (LED) soldered onto the instrument cluster electronic circuit board. The upshift indicator is serviced as a unit with the instrument cluster.

The upshift indicator gives an indication to the vehicle operator when the transmission should be shifted to the next highest gear in order to achieve the best fuel economy. 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 Powertrain Control Module (PCM) over the Programmable Communications Interface PCI data bus. The upshift indicator Light Emitting Diode (LED) receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (run-start) circuit whenever the ignition switch is in the ON or Start positions; therefore, the indicator 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. On models not equipped with a manual transmission, a unique version of the instrument cluster is used that does not include the upshift indicator. The instrument cluster will turn ON the upshift indicator for the following reasons:

- Bulb Test - Each time the ignition switch is turned to the ON position the upshift indicator is illuminated for about two seconds as a bulb test.

- Upshift Lamp-ON Message - Each time the cluster receives an upshift lamp-ON message from the PCM indicating the engine speed and load conditions are right for a transmission upshift to occur, the upshift indicator is illuminated. The indicator remains illuminated until the cluster receives an upshift lamp-OFF message from the PCM or until the ignition switch is turned to the OFF position, whichever occurs first. The PCM will normally send an upshift lamp-OFF message three to five seconds after a lamp-ON message, if an upshift is not performed. The indicator will then remain OFF until the vehicle stops accelerating and is brought back into the range of indicator operation, or until the transmission is shifted into another gear.

- Actuator Test - Each time the cluster is put through the actuator test, the indicator will be turned ON, then OFF again during the bulb check portion of the test to confirm the functionality of the indicator and the cluster control circuitry.

The PCM continually monitors the engine speed and load conditions to determine the proper fuel and ignition requirements. The PCM then sends the proper messages to the instrument cluster. For further diagnosis of the upshift indicator or the instrument cluster circuitry that controls the indicator, (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING). For proper diagnosis of the PCM, the PCI data bus, or the message inputs to the instrument cluster that control the upshift indicator, a DRB III scan tool is required. Refer to the appropriate diagnostic information.