Circuit Description

The throttle position (TP) sensors 1 and 2 are located within the throttle body assembly. Each sensor has the following components:

• A 5-volt reference circuit
• A low reference circuit
• A signal circuit

This provides the engine control module (ECM) with a signal voltage proportional to throttle plate movement. TP sensor 1 signal voltage at closed throttle is near the 5-volt reference and decreases as the throttle plate is opened. TP sensor 2 signal voltage at closed throttle is near the low reference and increases as the throttle plate is opened. If the ECM detects the TP sensor 1 signal voltage is not within the predicted range, DTC P0120 sets.