General Description

The Throttle Position (TP) sensor is a potentiometer connected to the throttle shaft on the throttle body. By monitoring the voltage on the signal line, the PCM calculates the throttle position. As the throttle valve angle is changed as the accelerator pedal moves, the TP sensor signal also changes. At a closed throttle position, the output of the TP sensor is low. As the throttle valve opens the TP sensor voltage increases. At Wide Open Throttle (WOT), the TP sensor voltage should be more than 4 volts. The PCM calculates the fuel delivery based on the throttle valve angle.

A broken or loose TP sensor may cause intermittent bursts of fuel from an injector and an unstable idle because the PCM thinks the throttle is moving. A hard failure in the TP sensor 5 volt reference or signal circuits should set DTC P0122 or DTC P0123. A hard failure with the TP sensor ground circuit may set DTC P0123 and DTC P0117. Once a DTC is set, the PCM uses an artificial default value based on the engine RPM and the mass air flow for the throttle position, and some vehicle performance returns. A high idle may result when DTC P0122 or DTC P0123 is set.

The PCM can detect intermittent TP sensor faults. DTC P1121 or DTC P1122 sets if an intermittent high or low circuit failure is detected. The PCM can also detect a shifted TP sensor. The PCM monitors the throttle position and compares the actual TP sensor reading to a predicted TP value calculated from the engine speed. If the PCM detects an out of range condition, DTC P0121 sets.