P0121

DESCRIPTION
The throttle position (TP) sensor mounts on the side of the throttle body and is connected to the throttle blade shaft. The TP sensor is a variable resistor (potentiometer) whose resistance changes according to the throttle blade shaft position. During acceleration, the TP sensor resistance decreases; during deceleration, the TP sensor resistance increases. The TP sensor also includes an idle position switch. The switch is closed in the idle position. The Powertrain Control Module (PCM) applies a reference voltage to the TP sensor and then measures the voltage that is present on the TP sensor signal circuit. The PCM uses the TP sensor signal to adjust the timing and injector pulse width. The TP sensor signal along with the MAP sensor signal is used by the PCM to calculate the engine load.

Troubleshooting Guide:

Circuit Diagram:

Test Procedure Part 1:

Test Procedure Part 2:

Test Procedure Part 3: