6 Symptoms of a Bad Throttle Position Sensor (and Replacement Cost)

(Updated on August 21, 2020)

A bad throttle position sensor is the last thing that you will ever wish to have on your ride. The purpose of a throttle position sensor is to keep your car running like it’s supposed to by controlling the throttle.

With the passage of time, the sensor will start to get worn and may eventually have to be replaced. The important question is how to identify any bad throttle position sensor symptoms so that you end up replacing the right sensor?

Honestly speaking, it is not easy to detect throttle position sensor issues. However, there are specific throttle position sensor signs to look for to help ensure you find the culprit.

What Does a Throttle Position Sensor Do?

The primary purpose a throttle position sensor (TPS) is to give information to the car’s computer about the throttle. It senses the air, heat, and light, and sends the information to the ECM which adjusts the throttle and fuel supply accordingly.

All vehicles have something called a “throttle” which controls how much fuel is allowed to flow into the engine. The throttle position sensor is what monitors the throttle position from the shaft.

Basically, this sensor is connected to a computer inside the vehicle which shares information sent by the driver. This information contains the actions of the driver such as accelerating, power steering and so forth.

So anytime you step on the gas pedal to accelerate your vehicle, the computer sends this information to the sensor so that the throttle knows how much fuel to let flow into the engine.

In the old days, there used to be a cable that was connected from the throttle to the accelerator. But now in the technological age, the car’s computer controls when the throttle opens and closes by the feedback it gets about the acceleration of the vehicle.

See Also: Drive By Wire Throttle Working Principle

Top 6 Bad Throttle Position Sensor Symptoms

A faulty throttle position sensor sends incorrect information to the ECM resulting in various issues in the engine, its performance, and fuel economy.

Below are common symptoms of a faulty TPS. In most of the cases, all of these symptoms will show together making it easier to detect the faulty component.

1) Car Jerks

no power steering

Jerking or bucking of the vehicle is the most common symptom of a bad TPS. These jerks can be experienced during hard acceleration or when under moderate load.

What makes diagnosing it tricky is that the bucks and jerks may be completely random and not even occur for some stretches of time. The reason this happens is that the ECM doesn’t get correct information from the TPS as to how much to throttle the car.

2) Idle Surging

engine idle speed

Idle surging can be caused due to other issues in the car, but if it happens in conjunction with other throttle position sensor symptoms, the culprit is often the TPS.

At idle, the ECM will not get the correct information and the throttle will variate randomly causing idle surges.

3) Check Engine Light

check engine light

The check engine light will randomly turn on and off even if the car is running smoothly without any jerks and stalling. This is often the first ever symptom of a bad TPS.

Using a code reader, you should be able to confirm whether a faulty TPS is the culprit or a different component. Diagnostic trouble codes P0120, P0121, P0122, P0123, and P0124 are what will commonly appear.

4) Engine Stalling

car shuts off while driving

The engine can stall for no reason and without any warning. This happens when the TPS gives incorrect information to the ECM. The engine can stall at high speed, at low speed, or even at idle.

5) Acceleration Issues

car hesitates when accelerating - gas pedal

A faulty throttle position sensor will not let your car accelerate normally. Though this doesn’t happen all the time. You may experience slow acceleration, acceleration surge at both high and low speeds, hesitation or delay in acceleration, and other related symptoms.

6) Problems Switching Gears

driving high altitude

The issues with acceleration can lead to gear transmission problems as the ECM doesn’t get the correct information about the acceleration. This leads to incorrect shift points which can cause both early or delayed shifts.

Can You Fix a Bad Throttle Position Sensor?

As soon as you see a mix of these throttle position sensor symptoms, you should test the TPS and if it isn’t functioning properly, it needs to be replaced. Unfortunately, a TPS cannot be repaired as it is a tiny sensor but the good news is that a new sensor “usually” isn’t too expensive so you can get back on the road soon enough.

Throttle Position Sensor Replacement Cost

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TPS replacement cost

If you need to have your throttle position sensor replaced, the cost will depend on the type of car you have. But the average cost of this replacement job isn’t that expensive.

The parts will cost you between $75 and $130 on average. The labor costs will be anywhere between $60 and $90, depending on the hourly rate of the mechanics. So in total, you can expect to pay between $135 and $220 for a throttle position sensor replacement.

Since replacing the TPS is fairly easy in most cases (depending on its location), you may be able to save yourself some time by doing it yourself. A quick search on Youtube is often all it takes.

Going to a dealership is going to cost you more so for most jobs (such as this one), we recommend you find a trustworthy independent mechanic whether by recommendations from family and friends or by reading online reviews.

And, of course, there may be taxes and fees added onto these costs which are determined by your location. But it’s still not too expensive when you consider everything else that could go wrong with your car.

Can You Drive With a Bad TPS?

Now you may be wondering when you’ll need to have your throttle position replaced. The simple answer is when your computer can no longer detect any signal from the throttle position sensor.

The will likely force your computer to stall the engine and only allow it to run at low RPMs, which means the car will only move at slow speeds. This is a safety feature enforced by the computer so that your engine doesn’t get too damaged.

Related: What is Limp Mode?

A throttle position sensor will generally fail simply from the wear and tear of driving the vehicle for many years. There is nothing you can really do to prevent this sensor from failing because it will just happen on its own.

The only thing you should do is have it replaced as soon as you notice these symptoms occurring in your vehicle.

35 thoughts on “6 Symptoms of a Bad Throttle Position Sensor (and Replacement Cost)”

  1. I just replaced my TPS & now all the symptoms are WORSE! Now when I take off it goes from 1st all the way to Overdrive almost immediately & when I floor it it won’t kick down to lower gear? I assume There is an adjustment I need to make. 1997 Infiniti QX4

    Reply
    • I’m not sure if there’s an adjustment required. Check the specifications of the factory service manual to know for sure.

      What was the reason for replacing the TPS? Perhaps it wasn’t the root cause of the issue.

      Reply
  2. I have a mystery I need help. Driving my 97 Oldsmobile cutlass supreme 3100 engine drove perfectly. Goin down the highway all of a sudden it does a lil jerk I loose all power to the accelerator won’t rev up and it dies pull over won’t start next day it fired right up. So I replaced the crank sensor drove perfect for a day then going down the highway same thing died won’t start. Replaced the ignition module drove perfectly for a day then same thing won’t start. I’m lost and out of ideas can anyone please help. The fuel pump is work I have spark the fuel filter brand new. I’m out of ideas. Could it be the coil packs or the throttle position sensor? Goes straight from running fine no loss of power no jerk no nothing to dead.

    Reply
  3. I have a 2004 trailblazer that has rpm surge in drive but runs fine in 3rd I had coil packs go bad so I replaced them. No check engine light and no codes could it be a bad throttle sensor

    Reply
  4. replaced throttle position sensor,and idle control valve on a 454 vortect,, cranks easy, runs but idles down low rpms and dies,, give it gas .it takes gas but backfires.. im lost,,

    Reply
    • throttle position sensor is bad,or there is a vaccume leak have it checked out before you buy the sensor,or maybe it needs adjustment if there aint no adjustment get a new one.

      Reply
  5. I have a 94 Silverado with a 5.0 & a automatic. It wants to idle low and die in gear at a stop light. New plugs, wires, vacuum lines, Idle Air Control valve. I cleaned the throttle body. Tons of power. Idles at around 400 rpm.
    Throttle position sensor ?

    Reply
  6. How do you determine if it is necessary to replace the entire throttle body vs. the PCV (valve) or TPS (sensor)?

    If the check engine codes are P0731 (trans), P0638 (throttle actuator) and P0420 (catalytic converter) might they be related?

    The car is a 2004 Outback (2.5L) that had the gas peddle assembly replaced less than six months ago. When it began behaving the same — could no longer accelerate past ~15mph — we figured it was the peddle again. (Transmission was also said to be in good shape around that same time when checked at an AAMCO.) The car has ~175K. What might cause it to fail — or is it possible that replacing the TPS and PCV would be sufficient?

    Reply
    • PCV valves are cheap and easy to replace. There are a couple tests you can look up to know if your PCV valve is bad.

      The throttle body is a mechanical component on the 2000 to 2003 Outbacks. I’m not sure if 2004 switched to electronic throttle control (i.e. drive by wire). If you have throttle cables like the 00-03 Outbacks did, check to make sure the throttle cables are adjusted properly.

      You may be able to physically inspect the throttle body assembly and cables to see if they are bad. Test the butterfly valve to make sure it opens and closes smoothly. The throttle body sits on top of the engine in the back and is easy to get to. You’ll probably want to replace the throttle body gasket while you’re in there.

      Reply
      • Thank you. This is very helpful, Sean. In answer to your question, think the 2004 is a drive-by-wire throttle (AT, 2.5L base model). What purpose does the throttle body gasket serve?

        This car has had a series of acceleration problems for which I’d appreciate your feedback:

        The first acceleration issue occurred in 2016 after the car abruptly failed to respond to the accelerator peddle while attempting to move forward after a stop light (dealer replaced peddle assembly). In October 2020 after the car lost acceleration and wouldn’t go past ~10mph (P21378), the peddle assembly was again replaced, this time by an independent shop. When the same symptoms appeared in February, I assumed the replacement peddle assembly was to blame — but the shop now wants ~$1500 to replace the throttle body (reason why I found your blog).

        January 2020 was the first time the car had an acceleration problem since the initial replacement of the accelerator peddle assembly in 2016. Last year at this time, the problem consisted of over-revving the engine when attempting to reach ~25mph (car threw a P1091 and had no power going up hills).

        A year ago this month, a Subaru dealer tried, unsuccessfully, to replace a “motor AY assembly” aka “tumble generator valve”. When they went to install the part the first time, they broke it. After obtaining a new one, they installed it but the code didn’t clear so they reinstalled the original and called with a recommendation to clean the intake manifold. (It didn’t make sense that the intake manifold would require cleaning since the head gaskets had been replaced in 2019, at which time the manifold presumably would have been inspected/cleaned.) In any case, the dealer wasn’t confident that cleaning the intake manifold would clear the code so they refused to guarantee the work (quoted $1K to do the job). As a second opinion, the car was towed from the dealer to an independent repair shop who replaced the intake manifold gasket — after reporting that the tumble generator valve was physically obstructed by improper alternator installation (a mobile mechanic had replaced the alternator shortly before the P1091 code had appeared).

        The car ran without issue from April last year until October when the accelerator peddle was replaced. It then ran OK from October until February, when the acceleration problem reappeared (P0731, P0638). With this in mind, some follow-up questions:

        When you mention checking to see if the butterfly valve is opening and closing smoothly, are you referring to the same butterfly valve the dealer replaced but then yanked?

        How closely positioned is the intake manifold and the throttle body?

        Is it possible that the dealer, the independent shop that discovered the obstructed linkage or even the shop that did the head gasket work in 2019 damaged or improperly reinstalled these parts, leading to the current situation?

        Lastly, are these acceleration issues in any way related to one another? In other words, might there be a common cause running through this and, if so, what else should be inspected or replaced?

      • The throttle body gasket keeps ambient air separate from air that has entered the intake through the air filter.

        Hmm, I could definitely see the TGV assembly causing the issues you’re experiencing if the TGVs were stuck closed. I was referring to the butterfly valve on the throttle body, not the TGVs the dealership was referring to.

        Here’s a great video that will show you what the TGVs look like. It’s geared toward a more performance oriented audience and shows the TGVs from a WRX, but you’ll get the idea of how they work. The TGVs sit between the intake manifold and the cylinder heads. At 2:23, he talks about the implications of pulling the TGV position sensors off without aligning them properly. I have a service manual on a 2004 Subaru Impreza handy (didn’t have one for an 04 Outback) and that manual specifically says not to remove the TGV position sensor, “since it cannot be adjusted during installation”. https://www.youtube.com/watch?v=3v54m161yXI

        The throttle body is mated to the back of the intake manifold. Take a look at this video around 1:55 and you’ll see where it is and what it looks like: https://www.youtube.com/watch?v=H-YfyXyPvrE

        It is possible that something was improperly repaired, causing the acceleration issues. I’m not sure. Unfortunately it’s really hard to say definitively what’s going on without some further testing. If it were my car, I would have to take the TGVs and throttle body off, inspect them, test sensors, etc. until I could start narrowing down the problem.

  7. Just bought a 94 cavalier in fairly good condition. For about two months it ran well, but then the engine light began to come on and after that, it began to be very difficult to start. I would turn the key to start but when I let go, the car engine died, never turning over.
    After I had both the fuel injector and the ignition coils replaced, it would start. But after two days it started rough, if at all, the engine only coming on if I held the ignition for half a minute or so without stepping on the gas. So I replaced the fuel filter and now it starts without having to hold the ignition for a prolonged amount of time, yet the engine starts off very rough, off time, for about one to two minutes, until the idle finally settles. I did purchase an idle control sensor (the car vibrates a lot in idle) but I’m beginning to wonder if I also need to change the TPS as well.

    Reply
  8. 1992 chevy v8 5.0 runs extemly rough at start . Hard to keep running but after sometime it will smooth out and run very smooth. Any ideas ? Replaced sensor at back of distributor and one on side of carb. Only thing not changed is the TPS.

    Reply

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