Throttle Position Sensor: Description and Operation

The Throttle Position (TP) sensor is mounted on the throttle body assembly. The sensor is actually 2 individual TP sensors within 1 housing. Two separate signal, ground and 5.0 volt reference circuits are used to connect the TP sensor assembly and the Throttle Actuator Control (TAC) module. The 2 sensors have opposite functionality. The TP sensor 1 signal voltage increases as the throttle opens, from below 1.1 volts at 0 percent throttle to above 3.7 volts at 100 percent throttle. The TP sensor 2 signal voltage decreases from above 3.9 volts at 0 percent throttle to below 1.2 volts at 100 percent throttle. Observe that the signal circuit for TP sensor 1 is pulled up to 5.0 volts and that the signal circuit for TP sensor 2 is pulled to ground within the TAC module. The TAC module converts these different signals to a common scale and continuously compares them to each other to verify proper system operation.

When the PCM detects a malfunction with the TP sensor circuits, one of the following DTCs will set:
^ DTC P1120 Throttle Position TP Sensor 1 Circuit
^ DTC P1220 Throttle Position TP Sensor 2 Circuit
^ DTC P1221 Throttle Position TP Sensors 1, 2 Performance




The TP sensor is mounted on the side of the throttle body opposite the air control valve. The TP sensor senses the throttle valve angle and relays that information to the PCM. knowledge of throttle angle is needed by the PCM to generate the required injector control signals (pulses).