Accelerator pedal position sensor

When the accelerator pedal position sensor malfunctions, the signal transmitted to the engine control unit may be erratic or absent, causing noticeable malfunctions while driving. The vehicle may exhibit slow or irregular throttle response, with jerks during acceleration, loss of power, or activation of a degraded mode that limits engine speed to ensure safety. The engine warning light may also come on, accompanied by warning messages on the dashboard, and the engine speed may vary unexpectedly or even remain at idle despite pressing the pedal. These anomalies reflect poor transmission of the driver’s intention to the ECU and require prompt verification in order to maintain responsiveness, safety and driving comfort.

Firstly, we strongly recommend that you visually inspect the accelerator pedal position sensor, i.e. its connector (for oxidation, bent pins, cut or damaged wires), the sensor itself (for dirt or liquid) and the pedal (to check that it moves freely).

Next, you can test that your sensor is working properly by checking its supply voltage (usually 5V supplied by the ECU) and ground (continuity and absence of parasitic resistance).

You can also measure the sensor’s output voltage (channel A and channel B) by gradually varying the pedal:

• At rest: typical voltage between 0.3 and 0.8V.
• At full stroke: typical voltage between 4.0 and 4.5V.

The variation must be linear and regular. Check the consistency of the two channels: they must change simultaneously but with different laws (functional safety).

If the above tests are inconclusive, then it would appear that you will need to replace your vehicle’s accelerator pedal position sensor.

Aaccelerator pedal position sensor can become defective for several reasons related to its mechanical or electronic operation or its environment. Natural wear and tear on the sensor, particularly on potentiometer models, can cause unstable or erratic signals. Electrical problems such as an oxidised connector, damaged wire or missing power supply can also prevent information from being transmitted correctly to the ECU. In addition, external influences such as humidity, dust, liquid splashes, extreme temperatures or excessive vibrations can damage the sensor or disrupt its operation. Finally, a fault in the ECU or carelessness when working on the wiring harness or pedal can cause inconsistencies in the signal. These causes, whether mechanical, electrical or environmental, compromise the accuracy of engine control and require careful checking to ensure the safety and reliability of the vehicle.

We recommend the following steps to replace your accelerator pedal position sensor as efficiently as possible and to limit possible mistakes.

1. Remove any trims or protective covers around the pedal if necessary.
2. Disconnect the sensor’s electrical connector.
3. Unscrew the sensor’s fasteners (usually 2 or 3 screws).
4. Carefully remove the sensor, taking care not to pull on the wires or the pedal.
5. On the new sensor, apply the manufacturer’s recommended non-conductive lubricant to the axle.
6. Position the sensor on the pedal and/or bracket.
7. Secure the sensor with the screws and tighten to the torque recommended by the manufacturer.
8. Reconnect the electrical connector, ensuring that it is properly engaged.
9. Check that the pedal moves freely and smoothly, without any sticking or excessive play.

In order to extend the life of your sensor, we strongly recommend that you follow these installation recommendations:

• Clean the throttle valve, as the new sensor alone will not compensate for a dirty throttle valve.
• Replace the return springs or silent blocks if they are worn, as incorrect pedal movement can distort the sensor measurements.
• After replacement, perform the pedal learning/calibration procedure if recommended by the manufacturer.