Transmission Shift Position Indicator Lamp: Description and Operation

GEAR SELECTOR INDICATOR
An electronic automatic transmission gear selector indicator is standard factory-installed equipment on this model. The gear selector indicator information is displayed in a Vacuum Fluorescent Display (VFD) unit. The VFD is soldered onto the cluster electronic circuit board and is visible through a window with a smoked clear lens located in the lower right quadrant of the cluster overlay. The dark lens over the VFD prevents the indicator from being clearly visible when it is not illuminated. The gear selector indicator displays the following characters from left to right: "P," "R," "N," "D," "2," and "1." Respectively, these characters represent the park, reverse, neutral, drive, second gear, and first gear positions of the transmission gear selector lever on the steering column. The VFD illuminates a rectangular box around the character that represents the currently selected lever position.

The gear selector indicator characters and graphics appear in the same blue-green color and at the same lighting level as the odometer/trip odometer information when illuminated by the instrument cluster electronic circuit board. During daylight hours (exterior lamps Off) the gear selector indicator VFD is illuminated at full brightness for clear visibility. At night (exterior lamps are On) the VFD lighting level is adjusted with the other cluster illumination lamps using the panel lamps dimmer knob on the headlamp switch. However, a "Parade" mode position of the panel lamps dimmer knob allows the VFD to be illuminated at full brightness when the vehicle is driven in daylight hours with the exterior lamps turned On. The gear selector indicator VFD is serviced as a unit with the instrument cluster.

The electronic gear selector indicator gives an indication to the vehicle operator of the transmission gear that has been selected with the automatic transmission gear selector lever. This gauge is controlled by the instrument cluster circuit board based upon cluster programming. The cluster circuitry automatically configures itself for the proper transmission and automatic transmission model based upon the hard wired transmission range sensor mux circuit input to the cluster. The gear selector indicator information is displayed by a dedicated Vacuum Fluorescent Display (VFD) unit on the instrument cluster electronic circuit board, and the VFD will not display the gear selector indicator information after the ignition switch is turned to the Off position. The instrument cluster circuitry configures the gear selector indicator VFD based upon the following inputs from the transmission range sensor:

- Transmission Range Sensor Multiplexed Input - The instrument cluster circuitry controls the gear selector indicator display based upon the resistance value of the hard wired input from the transmission range sensor. When the monitored input is within a proper resistance range, the instrument cluster illuminates a box in the VFD around the appropriate gear selector indicator position represented by that resistance. The indication of the gear selector indicator will remain illuminated until the input from the transmission range sensor changes, or until the ignition switch is turned to the Off position, whichever occurs first.

- Transmission Range Sensor Input Open Circuit - If the instrument cluster circuitry monitors an input from the transmission range sensor that indicates an open circuit, the cluster will blink all positions in the VFD. The VFD will continue to blink until the condition is resolved, or until the ignition switch is turned to the Off position, whichever occurs first.

- Transmission Range Sensor Input Short Circuit - If the instrument cluster circuitry monitors an input from the transmission range sensor that indicates the circuit is shorted to ground, the cluster will indicate all positions as selected in the VFD. The VFD will continue to indicate all positions selected until the condition is resolved, or until the ignition switch is turned to the Off position, whichever occurs first.

- Actuator Test - Each time the cluster is put through the actuator test, the gear selector indicator VFD will display all of its characters at once, then step through each character segment individually during the VFD portion of the test to confirm the functionality of the VFD and the cluster control circuitry.

The instrument cluster continually monitors the hard wired transmission range sensor multiplexed input. For further diagnosis of the gear selector indicator or the instrument cluster circuitry that controls this function, (Refer to ELECTRICAL/INSTRUMENT CLUSTER - DIAGNOSIS AND TESTING).