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
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.
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.
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.
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.
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.
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.
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.
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.
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.
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.
