Accelerator Pedal Position Sensor: Description and Operation

Accelerator Pedal (AP) Position Sensor







The function of the accelerator pedal (AP) position sensor is to provide the engine control module (ECM) and central electronic module (CEM) with information about the position of the accelerator pedal. This data is used by the engine control module (ECM) to deploy the shutter in the throttle unit to the correct angle.

The sensor consists of a plastic housing with two potentiometers, an AC/DC converter and circuits. The potentiometers are connected to a shaft which is affected by the position of the accelerator pedal (AP). The resistance in the potentiometers changes with the position of the accelerator pedal (AP).

The accelerator pedal (AP) position sensor transmits an analog and a digital signal (pulse width modulated (PWM) signal). The signals give information about the position of the accelerator pedal (AP). The digital signal is generated by the AC/DC converter in the sensor and is transmitted to the engine control module (ECM). The analog signal is transmitted central electronic module (CEM) and on to the engine control module (ECM) via the controller area network (CAN). The analog and digital signals are used at the same time by the engine control module (ECM) to regulate the throttle shutter angle.

The sensor is supplied with 12 V by the system relay via a fuse and is grounded in the car body. The digital signal is also used in conjunction with the analog signal for accelerator pedal (AP) position sensor diagnostics. The accelerator pedal (AP) position sensor signals can be read off using Vehicle Information and Diagnostics Application (VIDA). A diagnostic trouble code (DTC) is stored if the engine control module (ECM) detects a difference between the analog and digital signals. The engine control module (ECM) then uses a minimal value to ensure the function (limp home). The accelerator pedal (AP) position sensor is located on the accelerator pedal bracket.