Throttle Position Switch: Description and Operation

This switch, located on the throttle body, provides a voltage signal to the ECU when the throttle is either wide open or fully closed. The signal is sent either 10° before a wide open throttle condition, or 2° before it is fully closed. The wide open throttle signal is used to inform the ECU that the injectors must supply more fuel because of increased air flow. The closed throttle signal informs the ECU that the engine is in one of two conditions. If the ECU receives a closed throttle signal, and engine speed is greater than 1500 RPM, the ECU determines that a hard deceleration condition is occurring and responds by completely cutting off injection. If the ECU receives a closed throttle signal, and engine speed is less than 1500 RPM, the ECU determines that the engine is at or approaching an idle condition. It then realizes that it must maintain idle speed by energizing the idle speed regulator valve.