Failing Throttle Position Sensor: What It Means And How To Fix It

You might ignore TPS reports at the office, but your car’s TPS can’t be ignored.

byChris Teague|
Maintenance & Repair photo

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Certain things are a given in life, especially when it comes to cars. When you put your foot down on the gas pedal, it’s a given that your car will accelerate—until it doesn’t. There can be any number of issues that prevent acceleration or that cause your car to run roughly, but it can be hard to figure out what the problem is. 

One of the most common causes of those issues is your car’s throttle position sensor, also known as the TPS. The little sensor plays a big role in how much fuel your engine gets at any given point in time, and if it’s not functioning properly, you may notice changes in how your car runs and accelerates.

The Drive’s editors have diagnosed and replaced their car’s TPS before, and we’re here to help. It may be tempting to ignore the problem, especially if it’s only presenting itself intermittently, but we’re here to tell you that it’s not something you can bypass. 

Let’s get started.

The sensors can come in a variety of sizes and shapes., Depositphotos

What Is a Throttle Position Sensor and What Is Its Role? 

Before you can know if it’s going bad, you’ll need to actually know what a throttle position sensor is, and what it does.  

The sensor’s job is to determine the position of the throttle and communicate it to the engine control module (ECM). As part of a vehicle’s fuel system, the TPS plays an important role in determining the correct air-fuel mixture in the engine. Data from the TPS is used in conjunction with several other bits of information, such as airflow temperature, and engine speed. 

How Does a Throttle Position Sensor Work?

In the “old days,” throttle position sensors were physically attached to the throttle and would monitor its position through that contact. More recently, advances in technology have allowed the sensors to work without actually needing contact with the throttle. 

In some cases, the TPS uses what’s known as the Hall Effect to do its job, which involves magnetic fields that shift as the throttle opens and closes. The sensor reads those changes and communicates with the ECM to determine the exact throttle position. That reading is how your vehicle’s computer determines how much fuel to deliver to the engine at any given moment. This, of course, is a simplified version of the process, and may vary from make to make or model to model.

What Are The Symptoms and Signs Of a Failing Throttle Position Sensor?

You may not think much about your car’s TPS, but you’ll notice when it starts to go bad.

Lack Of Power

If your engine isn’t getting the fuel it needs, or is getting too much, you’ll notice that it doesn’t seem to be accelerating as it should be. When you put your foot down, the TPS should be screaming out for more fuel, but it won’t if it’s malfunctioning. If the opposite happens, your vehicle may surge forward when you’re not intending to speed up.

Trouble Accelerating

In a similar vein, you may notice that your car will accelerate, but won’t get past a certain speed. It might feel like the car just fizzles out after first or second gear and won’t upshift or go any faster.

Uneven Idle

If your car can’t maintain a constant engine speed when it’s sitting still, your TPS may be on its way out. A constant level of fuel delivery is necessary to maintain a steady idle.

Check Engine Light

On its own, a check engine light can mean absolutely nothing, or can mean something catastrophic is happening. If it’s seen in conjunction with any of the symptoms above, it’s a good indicator of TPS issues.

You might see a check engine light when the TPS starts to fail., Depositphotos

Can I Replace My Throttle Position Sensor At Home and How Much Will It Cost? 

Assuming there’s nothing else wrong with your fuel system or other sensors, you’ll likely be able to escape this situation without a major financial outlay. In most cases, having the TPS replaced will cost between $150 and $250, with the majority of that cost paying for labor.

The Basics of Throttle Position Sensor Replacement 

Estimated Time Needed: Less than one hour

Skill Level: Beginner to intermediate

Vehicle System: Electrical

Throttle Position Sensor Safety 

Just because it seems like an easy job, there’s no reason to skip out on safety.

  • Make sure you’ve disconnected the battery before starting work. It’s no fun finding out that you’re dealing with live wires the hard way.
  • Take care of your hands and eyes here by wearing safety glasses and gloves.
  • Park your car on level ground anytime you’re going to be working under the hood. The last thing you want is to have to chase a car down the street.
  • If you don’t have a safe parking space or garage to work in, try to move to a quiet parking lot or place away from traffic and moving vehicles. 

Everything You’ll Need To Replace a Throttle Position Sensor

Grab your safety gear and screwdriver set, and dive in!

Tool List

Parts List 

  • Replacement throttle position sensor

You might need your VIN to find the correct throttle position sensor, especially if your make/model came with different powertrain options from the factory.

Organizing your tools and gear so everything is easily reachable will save precious minutes waiting for your handy-dandy child or four-legged helper to bring you the sandpaper or blowtorch. (You won't need a blowtorch for this job. Please don’t have your kid hand you a blowtorch—Ed.)

You’ll also need a flat workspace, such as a garage floor, driveway, or street parking. Check your local laws to make sure you’re not violating any codes when using the street because we aren’t getting your ride out of the clink.

Put your foot down and go, right? , Depositphotos

Here’s How To Replace a Throttle Position Sensor

Let’s get started!

Disconnect the Battery

Before you start work, disconnect the battery’s negative terminal cable. This will prevent unwanted shocks to you and damage to other components under the hood.

Unplug Old Sensor

Once you’ve located the sensor’s position, you should be able to unplug the wiring harness that connects it to the vehicle’s computer system. Carefully unplug it, taking notice of any clips or connectors that need to be moved.

Remove Mounting Screws

Once it’s disconnected, you should be able to remove the screws that hold the sensor in place. Keep track of them in case you need to reuse them to install the new one.

Remove Old Sensor

Pull out the old sensor and dispose of it according to local regulations. 

Mount and Screw In New Sensor

Reversing the process, screw in the new sensor in the spot that the old one was pulled from.

Re-Plug Wiring Harness

Carefully re-plug the wiring harness into the new sensor, taking care to pay attention to clips and connectors that need to be aligned for proper installation.

Reconnect Battery Cables

Reconnect the negative battery terminal. Congrats! The job is done!

The Drive’s Pro Tips

It’s important to note here that your mileage may vary, depending on the make, model, and year of your vehicle. The TPS in older vehicles may be physically different or located in an odd spot, so it’s best for you to refer to your vehicle’s maintenance manual for pointers. 

We’ll also note that, in some cases, you’ll need to use a voltmeter to adjust the sensor. This can be done with the engine running, but will depend on the requirements of your vehicle, so again - check the manual!

FAQs About Throttle Position Sensor

You’ve got questions, The Drive has answers!

Q: I Don’t Have Time to Replace My Throttle Position Sensor, Can’t I Just Ignore It?

A: Do you like major, expensive repairs to your vehicle? Do you like breakdowns and unpredictable performance? We didn’t think so. Don’t ignore a bad TPS. It’s one thing to not be able to start your car in the morning, but having it break down on the highway is a whole different (and more dangerous issue) altogether.

Q: How Long Should My TPS Last?

A: The throttle position sensor is designed to last the lifetime of your vehicle, but things don’t always go according to plan. Any number of things can cause problems with the TPS, from electrical system issues to physical damage, none of which can be predicted ahead of time.

Q: I Replaced My TPS, But I’m Still Having Trouble. What Gives?

A: Remember that time, just a few moments ago, when we told you that you might need to adjust the sensor after installation? That could be your problem, along with a number of other issues. It’s best to have a pro diagnose the problem if you’re unsure of what you’re doing.

Q: Is the Throttle Position Sensor The Same As My Gas Pedal?

A: No, though they’re related. If your car has electronic throttle control, you may have what’s known as an APS, or accelerator pedal sensor.

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