Throttle Position Sensor: Description and Operation

Throttle Position (TP) Sensor:

PURPOSE
The Throttle Position Sensor (TPS) is a potentiometer connected to the throttle shaft on the throttle body and is nonadjustable. It senses the throttle valve angle and relays that information to the Powertrain Control Module (PCM). Knowledge of throttle angle is needed by the PCM to generate the required injector control signals (pulses).

OPERATION
The TP sensor electrical circuit consists of a 5 volts supply line and a ground line, both provided by the PCM. By monitoring the voltage on this signal line the PCM calculates throttle position. As the throttle valve angle is changed (accelerator pedal moved), the output of the TP sensor also changes. At a closed throttle position, the output of the TP sensor is low (approximately 0.29 to 0.98 volt). As the throttle valve opens, the output increases so that, at wide-open throttle, the Output voltage should be approximately 5 volts. A broken or loose TP sensor can cause intermittent bursts of fuel from the injector and an unstable idle because the PCM thinks the throttle is moving. A problem in any of the TP sensor circuits should set either a Diagnostic Trouble Code (DTC) 21 or 22. Once a DTC is set, the PCM will use an artificial default value for TP sensor and some vehicle performance will return. A high idle will result when either DTC 21 or DTC 22 is set.