Transmission Position Sensor/Switch: Description and Operation

IGNITION SWITCH-ST AND TRANSAXLE RANGE SWITCH [A/T]
When the ignition switch is in the ST position, the battery voltage is applied through the ignition switch and inhibitor switch to the ECM. If the selector lever is not in P or N position, the battery voltage will not reach the ECM.

Based on this signal, the ECM determines the automatic transaxle load and drives the idle speed control actuator to maintain optimum idle speed.