Bad Accelerator Pedal Sensor Symptoms, Causes and How To Fix It

The accelerator pedal position sensor (APP sensor) is most commonly used in the latest vehicle models. This article describes the bad accelerator pedal position sensor function, symptoms, and causes.

What is an Accelerator Pedal Position Sensor?

An accelerator pedal position sensor (APP sensor) is a mechanical device that measures the accelerator pedal position in a vehicle and transmits that data to the powertrain control module (PCM). The PCM utilizes this data to find how much air and fuel to mix together and send to the engine, eventually regulating the vehicle speed.

Accelerator Pedal Position Sensor

The accelerator pedal sensor usually contains two or three sensors in one unit that are located on the accelerator pedal assembly. These sensors contain a Hall effect, a potentiometer, or other technology to calculate the accelerator pedal position and change it into an electronic signal that is sent to the PCM.

The APP sensor has become one of the most important components of the modern engine control system, as it permits precise engine speed and throttle control. When the APP sensor goes bad or is damaged, it may lead to various issues, such as engine stalling, poor fuel efficiency, poor acceleration, or engine failure.

Symptoms of a bad Accelerator Pedal Position Sensor

When the accelerator pedal position sensor goes bad, it gives one or more of the below-given symptoms:

1) Rough Acceleration 

Poor Acceleration

The accelerator pedal sensor plays a critical role in the driver’s ability to control the vehicle’s acceleration. When the sensor malfunctions, the vehicle’s response to pressing the accelerator pedal is significantly delayed or reduced. This can pose a serious hazard on the road as it limits the driver’s control over the car.

Uneven acceleration is a clear indication of a malfunctioning accelerator pedal sensor, and it’s important to take action immediately to ensure safety.

If you notice uneven acceleration while driving, it’s recommended to pull over to a safe location and contact a professional technician to diagnose and resolve the issue promptly.

Continuing to drive the car with a faulty accelerator pedal sensor may result in sudden stops, which can lead to accidents and serious injuries.

2) Illuminated Check Engine Light

Check Engine Light, symptoms of a bad accelerator pedal sensor

If your accelerator pedal position sensor is faulty, one of the most noticeable symptoms is the illumination of the check engine light.

The accelerator sensor is an electronic component that communicates with the engine control module (ECM), and if there is an issue, it will trigger an error code that leads to the light’s illumination. Typically, a P2135 diagnostic trouble code will be logged for a faulty accelerator sensor.

It is crucial that all of a car’s electronic sensors function properly for the PCM to work correctly. However, keep in mind that there are many possible causes for the check engine light to come on. Therefore, it is recommended to consult a certified mechanic to accurately diagnose the issue and determine the root cause of the code.

3) Poor Fuel Economy

Bad Fuel Economy

A malfunctioning accelerator pedal sensor can contribute to poor fuel economy in a vehicle, but it’s worth noting that other factors can also impact fuel efficiency. For example, a dirty throttle body or a faulty throttle position sensor can also cause poor fuel economy.

4) Car Hesitate to Move

When the accelerator pedal position sensor malfunctions, it often leads to acceleration issues in the vehicle, making it difficult to achieve proper acceleration.

If you notice any abnormalities while driving your car, such as difficulty accelerating or poor performance, it is important to stop the vehicle immediately and seek the assistance of a professional to diagnose and repair the issue. Prompt attention to such problems can prevent further damage to the vehicle and ensure safe driving.

5) Poor Engine Performance

Poor Engine Performance

A malfunctioning accelerator pedal position sensor can have a negative impact on engine performance and fuel economy. In addition to monitoring throttle pressure and applying it to the throttle body, the APP sensor plays a vital role in stabilizing throttle control.

This sensor also helps regulate fuel pressure and communicates important data from the ECM to the vehicle’s throttle body.

However, if the sensor is damaged or if the wiring is frayed or corroded, it may not be able to transmit data to the ECM accurately. This can result in a significant reduction in engine performance, affecting the overall driving experience and fuel economy of the vehicle.

6) Vehicle Shifting Problems

Gear Shifting issues, signs of bad accelerator pedal position sensor

A malfunctioning accelerator pedal position sensor can lead to shifting problems in a vehicle, and this is one of the most noticeable symptoms.

When the sensor fails to function properly, it sends inaccurate information to the engine control module (ECM). This leads to problems when pressing the gas pedal, such as difficulty shifting or parking the vehicle.

7) Rough Idle

Rough Idle

A faulty accelerator sensor can cause rough idling in a vehicle, whereas a properly functioning accelerator sensor ensures a consistent fuel supply and smooth idling. When the sensor fails, it can disrupt the proper fuel supply, resulting in rough idling.

Read More: Rough Idle Symptoms and Causes

Causes of a Bad Accelerator Pedal Sensor

  • Wear and tear of the accelerator pedal sensor
  • Exposure to extreme temperatures or moisture
  • Damage or corroded electrical connections
  • Contamination inside the sensor
  • Extreme environmental factors such as extreme cold or heat
  • Manufacturing fault 

Read More: Axle Seal Leak Symptoms and Causes

Accelerator Pedal Position Sensor Location

The location of an accelerator pedal position sensor varies according to the vehicle model and engine type. The pedal position sensor is usually located near the accelerator pedal or connected to the throttle body. However, in some vehicle models, this sensor may be combined into the electronic throttle control system.

It is recommended to check your vehicle’s owner’s manual to quickly find the correct location of the accelerator pedal position sensor in your car model.

How to replace a bad Accelerator Pedal Position Sensor

  • Disconnect the negative battery terminal: Before starting, disconnect the negative battery terminal to prevent electrical shocks or damage to other parts.
  • Remove the bad accelerator pedal sensor: Locate the accelerator pedal sensor and disconnect the wire harness that transfers the electrical signal to the PCM. Press the knob and disconnect the sensor.
  • Remove the installation screw: It’s time to eliminate the mounting screw that fixes the sensor. Put the screws in a safe location if you want to reuse them.
  • Remove the bad APP sensor: Gently take away the bad sensor and check it properly.
  • Compare both sensors: Compare the new and old sensors to ensure they match, especially if you are replacing parts with aftermarket parts. Perform testing of the new sensor before installing it.
  • Install the new sensor: Install the new accelerator pedal sensor in the place where you removed the faulty sensor, and secure it with the mounting screw.
  • Replug the electrical connector: Replug the electrical connectors back into the new accelerator sensor. Inspect the connectors and align them for proper installation.
  • Reconnect the negative battery terminal: Reconnect the negative cable back into the battery and tighten it with a wrench set. Perform a test drive to ensure the accelerator pedal position sensor is functioning properly.

FAQ Section

Can I drive with a bad accelerator pedal position sensor?

While it is possible to drive with a bad accelerator pedal position sensor, it is not advisable. A malfunctioning sensor can cause several drivability issues, such as reduced acceleration and engine stalling. If the sensor fails entirely, your vehicle can go into limp mode, which limits its speed. In this case, you can safely drive the car back home without causing further damage. However, it’s important to address the issue promptly, as the sensor can deteriorate over time and eventually fail completely.

Is a throttle position sensor the same as an accelerator pedal position sensor?

The throttle position sensor and the accelerator pedal position sensor are two separate components with distinct locations in a vehicle. The accelerator pedal position sensor is installed on the accelerator pedal inside your vehicle, or the throttle position sensor is commonly installed inside or on the throttle body of your engine while.

Is it safe to drive with a faulty accelerator pedal position sensor?

Driving with a faulty accelerator pedal sensor can be dangerous, as the sensor plays a crucial role in transmitting the position of the accelerator pedal to the powertrain control module (PCM). The PCM uses this information to regulate the amount of air and fuel entering the engine. A faulty sensor can send incorrect data to the PCM, resulting in various drivability problems. Therefore, it is essential to address any issues with the accelerator pedal sensor as soon as possible to ensure safe driving.

How do I reset my accelerator pedal sensor?

Resetting the accelerator pedal position sensor varies depending on the vehicle model. However, in many cars, the resetting method of the accelerator pedal sensor is almost the same. To reset the gas pedal sensor, start by disconnecting and then reconnecting your vehicle battery. Now, switch on the ignition, completely press the accelerator pedal, and then release it. At the last, turn the ignition off. Following these steps should recalibrate the sensor.

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