Upshift Indicator - M/T: Description and Operation
UPSHIFT INDICATORAn 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 fuel 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 replaceable incandescent bulb and bulb holder unit located on 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 the cluster programming and electronic messages received by the cluster from the Powertrain Control Module (PCM) over the Chrysler Collision Detection (CCD) data bus. The upshift indicator bulb receives battery current on the instrument cluster electronic circuit board through the fused ignition switch output (st-run) circuit whenever the ignition switch is in the ON or Start positions; therefore, the lamp will always be OFF when the ignition switch is in any position except ON or Start. The bulb only illuminates when it is provided a path to ground by the instrument cluster transistor. On models not equipped with a manual transmission, the incandescent bulb and bulb holder unit are not installed at the factory when the vehicle is built.
The instrument cluster will turn ON the upshift indicator for the following reasons:
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 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. If the upshift indicator fails to light during normal vehicle operation, replace the bulb with a known good unit. For further diagnosis of the upshift indicator or the instrument cluster circuitry that controls the indicator, (Refer to INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING Testing and Inspection). For proper diagnosis of the PCM, the CCD 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.