Symptoms of a Bad or Failing Throttle Position Sensor

throttle position sesnsor

The throttle position sensor is part of your vehicle fuel management system that helps ensure your engine is getting the right mixture of fuel and air at every moment. The throttle position sensor provides the most direct signal to the fuel injection system of what power demands are being made of the engine. The TPS signal is measured and combined many times per second with other data such as air temperature, engine RPM, (actual) air mass flow, and how quickly the throttle position may be changing. These data determine precisely how much fuel to inject into the engine for the next few milliseconds. This is done repeatedly, many times per second. If the throttle position sensor and its other sensor partners do their job correctly, your car accelerates, cruises, or coasts down smoothly and efficiently, as you expect.

The throttle position sensor can fail in several ways, all of which result in poor fuel performance at best, and performance limitations that may create safety hazard for you and other motorists at worst. This sensor can fail gradually, or all at once. In most cases, the Check Engine Light is illuminated if a TPS failure is detected. Also, most manufacturers provide a “limp home” mode of operation with reduced power if a failure is detected. This would at least allow getting off a busy highway in a safer manner. Once the TPS begins to fail, even partially, you’ll need to replace it right away. Replacing the TPS will include clearing relevant fault codes, and may require software re-programming of the new TPS module to match other engine management software. This is all best left to a professional mechanic who can provide you with a diagnosis, and then install the correct replacement part.

Here are some common symptoms of a bad or failing throttle position sensor to watch for:

1. Car won’t accelerate or lacks power when accelerating

It may feel as though the car just doesn't accelerate as it should. It may accelerate smoothly, but lack power. On the flip side, it may be that your car suddenly speeds up while you’re driving, even if you haven’t pressed the accelerator. If these symptoms occur, there's a good chance you've got a problem with the throttle position sensor.

2. Engine won’t idle smoothly, idles too slow, or stalls

If you start to experience engine misfires, stalling, rough idling, or poor running at a stop light, these can also be warning signs of a failing throttle position sensor. You don't want to wait to get this checked out!

3. Car accelerates, but won’t exceed a relatively low speed (20-30 mph) or shift up

This is another failure mode of the TPS, which indicates that it is falsely limiting the power being requested with your accelerator pedal foot. This symptom often goes hand in hand with lack-of-power behavior.

4. Check Engine Light comes on, accompanied by any of the above behaviors

The Check Engine Light may come on if you’re having issues with your throttle position sensor. This isn’t always the case though, so don’t wait for this to happen before you get it checked out. If you have any of the above symptoms, have your vehicle checked for trouble codes to make sure that is the problem.

The throttle position sensor is key to getting the desired power and fuel efficiency from your vehicle in any driving situation. As the symptoms listed above make clear, failure of this component has serious safety implications, and must be checked out immediately by a qualified mechanic.

The statements expressed above are only for informational purposes and should be independently verified. Please see our terms of service for more details

Ask a Mechanic
(100% Free)

Have a car question? Get free advice from our top-rated mechanics.

Ask A Mechanic
Over 10,000 questions answered!

More related articles

P0052 OBD-II Trouble Code: HO2S Heater Control Circuit High (Bank 2 Sensor 1)
P0052 code definition HO2S Heater Control Circuit High (Bank 2 Sensor 1) What the P0052 code means This code is seen when the Engine Control Module (ECM) tries to control the...
Insurance Requirements for Car Registration in Kentucky
The Kentucky Transportation Cabinet requires that all drivers in Kentucky carry liability automotive insurance, or “financial responsibility” in order to operate a vehicle legally and maintain vehicle...
Rules of the Road For Iowa Drivers
Driving on the roads requires knowledge of the rules, many of which are based on common sense and courtesy. However, even though you know the rules in...

Related questions

Q: There is a jerking that seems to be coming from the throttle sensor

Without more detail of the symptoms, there are several possibilities that could cause this. As you may know, there are a few different sensors related to the fuel delivery in your car's intake system - one of which is the...

Q: Warning regarding throttle and limp home mode

Hello. This is the first sign of a bad throttle body. This is a common failure on this vehicle. When the throttle motor or position sensor fails this occurs as the computer can no longer control the throttle. Most of...

Q: Transmission - 2003 Chevrolet Trailblazer

This may be caused by a variety of things in addition to the TPS. These possibilities could include a bad catalytic converter, internal damage on the transmission, or many other engine sensor problems. For starters, I would recommend checking the...