Bad Accelerator Pedal Position Sensor: Symptoms and Replacement

The accelerator pedal position sensor is crucial to your vehicle’s fuel efficiency and road performance. Its readings guide the electronic throttle control (ETC) that manages the fuel injection system. While designed for long-lasting service, the sensor can still fail without warning. A faulty pedal position sensor will cause issues until you replace it with a new part. Read on and familiarize yourself with the most common symptoms of a bad accelerator pedal position sensor.

What’s the Accelerator Pedal Position Sensor?

The accelerator pedal position sensor is one of the parts that comprise the gas pedal. It’s also called the accelerator pedal sensor or APP sensor.

Most pedal position sensors are non-conductive devices. Their internal components don’t need to come into physical contact during operation.

Typically, an accelerator pedal position sensor comprises a stator and a rotor. The stator is the more complex component, possessing several coils and an electronic evaluation unit that checks the sensor’s status.

Only automatic vehicles with an ETC possess an accelerator pedal position sensor. Other automatic vehicles rely on different sensors to measure the throttle opening and the volume of air passing through it. Meanwhile, manual vehicles use a mechanically-based approach to control the throttle.

Faulty Accelerator Pedal Position Sensor Symptoms

Most accelerator pedal position sensors will last for your vehicle’s entire service life. However, the device can prematurely wear out from heavy use or fail after taking severe damage.

Here are some of the most common symptoms of a faulty accelerator pedal position sensor:

Check Engine Light Illuminates

The power control module (PCM) will activate the check engine light if it detects any issues with the engine. A malfunctioning accelerator pedal position sensor can trigger this warning light when it sends either incorrect information or no readings to the ETC.

If the ETC gets the wrong data from the accelerator pedal, it might add too much or too little fuel to the blend. The engine will run lean or rich. A bad sensor can also deprive the ETC of the readings it needs to tweak the air-fuel mixture. Either way, the resulting engine issues will illuminate the check engine light.

Engine Responds Erratically to the Accelerator Pedal

Does your vehicle speed up or slow down without any consistency? There might be an issue with its accelerator pedal position sensor.

Typically, if the redundant sensors don’t agree, a warning light (wrench light or throttle body light) will illuminate and throttle action will be greatly reduced

Usually, the pedal position sensor will immediately inform the ETC about any changes in the pedal’s location. The ETC will waste no time adjusting the electronic throttle plate angle, which in turn affects fuel delivery to meet the need for higher or lower speed.

Higher Engine Idle Speed

A faulty accelerator pedal position sensor can make an idling engine run at higher revolutions per minute (RPM) than expected. During idle periods, the engine operates at reduced RPM to save fuel while generating enough power to run its systems.

Unfortunately, inaccurate readings from the accelerator pedal position sensor can make the ETC increase the fuel supply. The influx of excess gasoline or diesel will increase the RPM, leading to higher fuel consumption and wearing out the engine faster.

Limp-Home Mode Engages

When the PCM detects a severe issue, it will put your vehicle in limp-home mode. The engine will only run at low performance to avoid straining damaged parts, leading to a snail’s pace. Furthermore, the PCM will disable power-hungry systems like the HVAC to reduce the load on the engine.

In some cases, the faulty accelerator pedal position sensor can cause so much trouble that the PCM decides to put the engine in limp-home mode. You must replace the bad sensor and clear the associated diagnostic codes to return your vehicle to normal.

What Makes the Accelerator Pedal Position Sensor Fail?

Several possible reasons can make an accelerator pedal position sensor fail. One of them is a damaged sensor element. This component relies on a wiper arm to keep it clean. Unfortunately, the wiper arm can slowly but steadily wear away at the sensor element until the latter becomes too damaged to operate.

Another common reason for sensor failure is an issue with its cabling. The accelerator pedal position sensor uses cables to connect to the ETC. These cables and their connectors can develop problems like corrosion and fraying.

Insufficient voltage and ground supply can also make an accelerator pedal position sensor fail. Like any electronic device, the sensor needs a steady current supply for power. It also needs grounding to protect against surges.

Last but not least is a faulty electronic evaluation unit. This component checks the accelerator pedal position sensor for any issues. However, it isn’t immune to failure. A damaged or worn-out evaluation unit can flag the entire sensor as faulty.

What Does the Accelerator Pedal Position Sensor Do?

The accelerator pedal position sensor tracks the gas pedal’s position at any given time. When you step on the pedal, the device will update the ETC about the positional change.

Redundant accelerator pedal sensors are used to prevent possible runaway conditions. But one wrinkle is that the redundant sensors put out slightly different signals. Some vehicles will have a “mirrored” signal from sensor to sensor and others will have a lower voltage signal on one sensor and higher voltage signal on the second sensor.

Redundant accelerator pedal sensors are used to prevent possible runaway conditions. But one wrinkle is that the redundant sensors put out slightly different signals. Some vehicles will have a “mirrored” signal from sensor to sensor and others will have a lower voltage signal on one sensor and higher voltage signal on the second sensor.

–Richard McCuistian, ASE Certified Master Automobile Technician

This is to differentiate between the two sensor signals for fault detection. If one of the two sensors were to fail on a system designed so that both sensors read exactly the same or if the sensor output wires were to short together, the ECM/PCM would have no way of knowing about the failed sensor or circuit. With the sensor signals operating redundantly but in slightly different ranges, a fault is easily detected.

How Much Does a Replacement APP Sensor Cost?

If you plan to get a new accelerator pedal position sensor, prepare to pay anywhere between $10 and $800. The price can vary depending on factors like your vehicle’s make and model and the product’s brand and manufacturer.

Where To Get a New Accelerator Pedal Position Sensor

Now that you’ve figured out the underlying cause behind your vehicle’s problems, it’s finally time to do something about it. Driving around with a bad accelerator pedal position sensor can damage your engine, so you’ll want to replace it as soon as possible. Thankfully, you can easily order a new accelerator pedal position sensor here at CarParts.com.

With a wide range of products and an easy-to-use interface, CarParts.com eliminates the hassle of buying a new accelerator pedal position sensor. All you have to do is input your vehicle’s year, make, model, and engine in our handy vehicle selector, and browse through our available products.

You don’t have to worry about quality either. Our accelerator pedal position sensors are all sourced from the best manufacturers in the industry.

What are you waiting for? Shop now at CarParts.com and get the best bang for your buck!