Transmission Position Sensor/Switch: Description and Operation

TRANSMISSION PARK/NEUTRAL SWITCH-PCM INPUT
The park/neutral switch is located on the transmission housing and provides an input to the Powertrain Control Module (PCM), This will indicate that the automatic transmission is in Park, Neutral or a drive gear selection. This input is used to determine idle speed (varying with gear selection), fuel injector pulse width, ignition timing advance and vehicle speed control operation.

The center terminal of the park/neutral position switch is the starter-circuit terminal. It provides the ground for the starter solenoid circuit through the selector lever in PARK and NEUTRAL positions only. The outer terminals on the switch are for the backup lamp circuit.