Accelerator Pedal Position Sensor
The Accelerator Pedal Position (APP) sensor allows the Powertrain Control Module (PCM) to determine the driver requests for vehicle speed, acceleration and deceleration. The PCM uses this information, together with information from the Anti-lock Brake System (ABS) control module and the Transmission Control Module (TCM), to determine the torque demand from the engine via injection control.
The APP sensor is integrated into the accelerator pedal, which is attached to the passenger compartment bulkhead. A six pin electrical connector provides the interface with the vehicle harness.
The APP sensor consists of a twin track rotary potentiometer integrated into the mounting bracket of the accelerator pedal. The APP sensor receives two separate electrical supplies and generates two different outputs. Both tracks are analogue output signals connected to the PCM. Both signals contain the same positional information, but the secondary track has half the voltage output of the primary track.
If there is a fault with the primary track, the secondary track is used and the vehicle/engine response to pedal demand will be sluggish. If both analogue signals have a fault, the engine adopts a constant engine speed of 1300 Revolutions Per Minute (RPM) to allow the vehicle to move. Torque application and reduction of engine speed back to normal idle speed can be subsequently controlled via brake pedal switch operation.
For additional information, Refer to: SPEED CONTROL
The PCM constantly checks the range and plausibility of the two signals and stores a Diagnostic Trouble Code (DTC) if it detects a fault.