Transmission Position Sensor/Switch: Description and Operation

With the ignition switch in ON (II) or START (III), voltage is applied to the A/T gear position indicator. The A/T gear position switch provides a ground for each position. As an input is grounded, its indicator light comes on. If you select R, for example, ground will be provided to the input of the A/T gear position indicator, and the R indicator will come on.

With the headlight switch in PARK or HEAD, voltage is applied to the RED/BLK wire terminal. This changes the indicator panel illumination from fixed to controlled by the dash lights dimmer input through the RED wire.

When the powertrain control module (PCM) detects an abnormality in the automatic transmission control system, or when you request diagnostic trouble codes through the service check connector, the PCM will make the D4 indicator ('97-'98 models) or the D indicator ('99 model) light blink.

For '99 model vehicles, when the O/D OFF switch is closed it sends a ground signal to the PCM. The PCM in turn, provides ground for the O/D OFF indicator bulb inside the gauge assembly and turns on the indicator light.