How to Tell if Accelerator Pedal Position Sensor is Bad

How to Tell if Accelerator Pedal Position Sensor is Bad – Modern cars are designed with a wide range of sensors that ensure safety, manage other components of the car, and ensure driving is smooth and easy.

The Accelerator Pedal Position (APP) sensor is designed to detect the position of the gas/accelerator pedal and send that information to the engine control unit (ECU). This information is used by the control unit to adjust the throttle valve’s position and the air-fuel ratio when the accelerator is pressed.

As one of the most vital sensors in a car, if there is a problem with the accelerator pedal position sensor, the car will malfunction and will show several symptoms. The APP sensor is made to last for a long time but due to the heat in the car cabin and prolonged usage, it can fail.

It is important to know the signs of a faulty accelerator pedal position sensor beforehand so that when you are faced with issues like this, you will be able to take prompt action.

This article helps you to know if your accelerator pedal position sensor is bad.

What is Accelerator Pedal Position Sensor?

The accelerator pedal position sensor is a car sensor that monitors the movement of the gas pedal and sends this information to the ECU. The ECU then uses this information to adjust the air-fuel ratio and throttle valve position for a hassle-free drive.

The APP sensor acts as a connection between a driver and the control unit. When the driver presses the gas pedal, the sensor sends information to the ECU to adjust the air-fuel ratio and the position of the throttle valve as well, to allow an appropriate quantity of air and fuel into the engine.

The APP sensor informs the control unit of how much the gas pedal is pressed and enables it to send the right amount of air and fuel to the engine. The APP sensor also helps the control unit determine how fast or slow the car should move when the gas pedal is depressed.

How does the Accelerator Pedal Position Sensor work?

The working principle of the accelerator pedal position sensor is easy to understand. When a driver presses on the gas/accelerator pedal to increase the speed of the car, the APP sensor at this point monitors the position of the gas pedal and sends the signal to the ECU.

When this signal is received by the control unit, the ECU then determines the ratio of air and fuel to be directed to the engine and opens the throttle valve using information from the accelerator pedal position sensor, RPM, air temperature, and car speed.

The gas pedal is connected to the throttle body and the throttle body determines how much air gets into the engine. As the gas pedal is being matched and the APP sensor sends signals of how much the pedal has been pressed to the engine control unit, the ECU measures the amount of air needed and adjusts the throttle valve accordingly.

The ECU also controls the amount of fuel the fuel injectors release to ensure there is a balance in the engine’s air-fuel mixture.

How to Tell if Accelerator Pedal Position Sensor is Bad

The symptoms of a faulty accelerator pedal position sensor are many.

These symptoms are usually glaring, as they will affect the responsiveness of the pedal, gas mileage, and the overall performance of the car.

Here’s a list of signs to watch out for.

Check engine light comes on

One major symptom of a faulty APP sensor is the illumination of the check engine light.

Modern cars are designed with different sensors and a central control unit to monitor these sensors. If there is a problem with one of the sensors, the accelerator pedal position sensor, in this case, the check engine light will illuminate.

Acceleration problems

If the acceleration pedal position sensor is bad, it will reduce your car’s ability to accelerate when it is supposed to.

Sometimes, the car might accelerate to a certain point when the pedal is pressed down and fails to accelerate further, thereby limiting your car’s speed. This occurs because of the inability of the APP sensor to send correct positioning signals to the control unit.

Car jerks when the gas pedal is pressed down or faulty automatic transmission shifting

If the APP sensor is faulty, it will send wrong signals to the automatic transmission unit of your car which will make it difficult to shift gears.

When you press down your gas pedal with a faulty sensor, it will delay the signals that are supposed to be sent to the transmission unit or will send different wrong signals causing the car to jerk.

Low gas mileage

Low gas mileage is one problem a bad accelerator pedal position sensor will cause.

When the APP sensor is failing, it can send the wrong data to the control unit.

The control unit will convert this data and miscalculate the quantity of fuel/gas to send to the engine. This will reduce your gas mileage because the ECU can direct an excess amount of fuel to the engine when it is not needed. This extra fuel will burn out and will be wasted.

Rough idling

A faulty APP sensor could be the reason your car has rough idles. The normal engine runs at 600 to 1000 RPMs while idling depending on your car model. At these RPMs, which tend to be the normal engine RPM, the engine idles smoothly.

A faulty APP sensor can outrightly increase or reduce the engine’s RPMs, leading to a rough idle.

Low engine power

When the accelerator pedal position sensor is faulty, the engine’s power will be low. A faulty APP sensor will reduce car speed, cause weak or heavy acceleration, and poor engine performance.

Causes of a Bad Accelerator Pedal Position Sensor

The APP sensor can fail due to several reasons including,

  • Corroded cables and faulty connections in the sensor.
  • Bad voltage and ground supply.
  • A faulty unit in the sensor.
  • Contamination from dirt or water.

Steps to test the Accelerator Pedal Position Sensor

Before diagnosing a problem with the APP sensor, you must have carried out a test to know exactly what the problem is.

There are two basic ways to test the APP sensor. One way is using a scan tool to scan your car and look out for error codes, while another is using a multimeter to test the voltage output of the sensor.

Here are some steps to take when testing the accelerator pedal position sensor.

  1. Locate the APP sensor: This is the first thing to do when you want to test the sensor. You can find the APP sensor under the driver’s side dashboard, inside the gas pedal.
  1. Inspect the wiring harnesses and other parts of the APP sensor. Check for loose wire connections, rust, or corrosion as these can be the reasons for your APP sensor’s failure.
  1. Check for dust or other forms of contaminants on the surface of the sensor. Since the sensor is in the cabin, close to the driver’s seat, it can be affected by sand, dirt, or water. These contaminants can lead to it going bad.
  1. Test the wire with a multimeter to know if they are still working. Before doing this, set the meter to the Ohms scale then activate the beep.
  1. Shift the wiring harness a bit to get full access to the connectors.
  1. Place the red probe of the multimeter on individual connectors, while you ground the black probe on the vehicle’s body.
  1. You should turn off the ignition while using the multimeter to test the different connectors in the sensor.
  1. The reading on the multimeter should be less than 5 Ohms. However, if there is a significant difference in the reading of each connector, then the problem is from the APP sensor’s wiring and connection.
  1. There are two more wires to be tested that were not tested earlier. Turn the ignition to the ‘ON’ position while doing this.
  1. Locate a black and red wire in the sensor and test them. The reading should be between 4.9 and 4.8, anything lower than these indicates the wiring harness is having some issues.
  1. You can also connect a scan tool to extract codes from the engine control unit. This should be done with the ignition switch in the “ON” position.

How to fix a faulty Accelerator Pedal Position Sensor

Fixing a faulty APP sensor is an easy task to carry out as long as you have the right tools at hand.

A bad APP sensor cannot be repaired, so what you are doing is a replacement.

Here are steps to replace a faulty APP sensor.

  1. Get a screwdriver set, safety glasses, voltmeter, and work gloves.
  2. The replacement APP sensor should be handy as well.
  3. Disconnect the negative terminal from the battery before starting to avoid shocks or electrical jolts.
  4. Carefully remove the wiring harness, and installation screws and keep them safe before removing the old APP sensor.
  5. Install the new APP sensor and reconnect all disconnected wirings and connections.
  6. Finally, reconnect the negative battery terminal and take your car for a test drive.

Cost of replacing a faulty Accelerator Pedal Position Sensor

Depending on your car’s model or make, replacing the APP sensor can cost between $100 and $300.

The sensor itself costs between $50 to $200 while the cost of labor is an additional $50 to $100 at an auto repair shop.

Frequently Asked Questions

Where is the Accelerator Pedal Position Sensor located?

The APP sensor can be found inside the accelerator/gas pedal of a car. The gas pedal is located inside the cabin, just under the driver’s side dashboard.

How can I reset my Accelerator Pedal Position Sensor?

Resetting the APP sensor depends mostly on your car model. For most car models, all you need to do is disconnect and reconnect your car’s battery. This is followed by turning the ignition on and pressing down the gas pedal for a while. When these activities have been completed, turn off the ignition and your APP sensor will go back to default.

Can I drive with a bad Accelerator Pedal Position Sensor?

No! You should not drive with a bad APP sensor. The APP sensor is supposed to send the right information to the ECU for it to determine the amount of fuel and air to be sent to the engine for smooth acceleration. However, a faulty APP sensor will send wrong signals which makes driving stressful and can lead to hazardous situations.

How often should I replace my Accelerator Pedal Position Sensor?

The APP sensor is designed to last the lifespan of your car so there is usually no specific replacement period. However, like every other component of a car, this sensor can wear out and start malfunctioning. It is important to replace the sensor once you notice any symptoms of failure.

Can a bad Accelerator Pedal Position Sensor damage my Car?

A faulty accelerator pedal position sensor will not damage your car. It will only lead to some malfunctioning until you replace it. A faulty APP sensor will affect acceleration, gas mileage, and can also lead to other driving issues.