Accelerator Pedal Position Sensor: Description and Operation

ACCELERATOR PEDAL POSITION (APP) SENSOR




The accelerator pedal position (APP) sensor assembly (2) is fastened to the accelerator pedal assembly and attached to the brake pedal bracket (1). The APP sensor assembly contains two APP sensors that are operated by the accelerator pedal movement. The APP sensors 1 and 2 are potentiometer type sensors each with 3 circuits:
- A 5-volt reference circuit
- A low reference circuit
- A signal circuit

The APP sensors are used to determine the pedal angle. The powertrain control module (PCM) provides each APP sensor a 5-volt reference circuit and a low reference circuit. The APP sensors provide the PCM with signal voltage proportional to the pedal movement. APP sensor 1 signal voltage is low at the rest position and increases to near the 5-volt reference as the pedal is applied. APP sensor 2 signal is low at rest and also increases as the accelerator pedal is applied. APP sensor 2 increases at a different rate to approximately half the reference voltage. The APP sensor 1 is responsible for providing the actual pedal position to the PCM. The PCM then sends a throttle position target value to the TAC control module. APP sensor 2 provides a backup value to the APP sensor 1.

Throttle Body Assembly:

The throttle body functions similar to a conventional throttle body with the following exceptions:
- An electric motor opens and closes the throttle valve.
- The TAC module is an integral part of the throttle body assembly.
- The throttle valve is spring loaded and the default position is slightly open.
- There are 2 individual throttle position (TP) sensors integral to the TAC module cover.

The TP sensors are used to determine the throttle plate angle. The TP sensors provide the TAC module with a signal voltage proportional to throttle plate movement. Both TP sensor signal voltages are low at closed throttle and increase as the throttle opens. TP sensor 1 determines the actual throttle valve position. TP sensor 2 provides a backup value for TP sensor 1.