Throttle Position Sensor: Description and Operation

The nonadjustable TP sensor is mounted on the side of the throttle body opposite the throttle lever. It senses the throttle valve angle and relays that information to the PCM. Knowledge of the throttle angle is needed by the PCM to generate the required injector control signals (pulse). For further information, Refer to In formation Sensors/Switches 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 throttle position. As the throttle valve angle is changed (accelerator pedal moved), 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 output increases so that at Wide Open Throttle (WOT), the output voltage should be above 4.0volts.




The PCM calculates fuel delivery based on throttle valve angle (driver demand). A broken or loose TP sensor may cause intermittent bursts of fuel from an injector and unstable idle because the PCM thinks the throttle is moving. A hard failure in the TP sensor 5.0 volt reference or signal circuits should set either a DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage. A hard failure with the TP Sensor ground circuit may set DTCs DTC P0107 Manifold Absolute Pressure (MAP) Sensor Circuit Low Voltage, DTC P0112 Intake Air Temperature (IAT) Sensor Circuit Low Voltage, DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage, or DTC P0117 Engine Coolant Temperature (ECT) Sensor Circuit Low Voltage. Once a DTC is set, the PCM will use an artificial default value based on engine RPM, engine load and mass air flow for throttle position and some vehicle performance will return. A high idle may result when either DTC P0122 Throttle Position (TP) Sensor Circuit Low Voltage, or DTC P0123 Throttle Position (TP) Sensor Circuit High Voltage is set.




The PCM can detect intermittent TP sensor faults. DTC P1121 Throttle Position (TP) Sensor Circuit Intermittent High Voltage, or DTC P1122 Throttle Position (TP) Sensor Circuit Intermittent Low Voltage will set it an intermittent high or low circuit failure is being detected.




The PCM can also detect a shifted TP sensor. The PCM monitors throttle position and compares the actual TP sensor reading to a predicted TP value calculated from engine speed. If the PCM detects an out of range condition, DTC P0121 Throttle Position (TP) Sensor Performance will be set.

The nonadjustable TP sensor is mounted on the side of the throttle body opposite the throttle lever. It senses the throttle valve angle and relays that information to the PCM. Knowledge of the throttle angle is needed by the PCM to generate the required injector control signals (pulse). For further information, Refer to In formation Sensors/Switches Description.