Symptoms of Bad Throttle Position Sensor: Diagnose and Fixes

Thousands of system components work together in harmony to make your vehicle engine provide peak performance the way it’s supposed to, and the throttle position sensor (TPS) is one of those components that are often overlooked. The throttle body is an essential component of fuel management that monitors the air that goes to the engine. The collected data that enables the throttle position sensor to monitor air into the engine determines precisely the amount of gas to inject into the engine at any given time.

Suppose the throttle position sensor and its related partners carry out their duty properly. In that case, your vehicle will accelerates, coast, and cruise nice and smoothly as you expect while providing peak performance. On the other hand, when the throttle position sensor fails, you will notice symptoms of bad throttle position sensor that can result in performance limitations, poor fuel economy, erratic idling, to name just a few.

Symptoms of bad throttle position sensor

There are various symptoms that will pop up on your vehicle to tell the driver of a failing or defective throttle position sensor. Some of these signs can also be a clogged throttle body symptoms. At the same time, others indicate a variety of other engine problems. Chances are, if you experience two or more of these symptoms, you have a lousy throttle position sensor.

throttle position sensor test

1. Check engine light

The throttle position sensor plays a significant role during the internal combustion process. If this car sensor fails, you’ll experience a drastic poor engine performance and rough acceleration; thus, the ECU will detect this fault and trigger the engine warning light on the dashboard. That way, you will know that your engine has a fault that needs attention.

2. Car won’t accelerate or weak acceleration

With a bad TPS in place, your vehicle may seem as though it doesn’t accelerate as it should, and hesitates, jerks, or won’t run smoothly. The vehicle engine may give a good acceleration but lacks engine power. On the other hand, it may suddenly accelerate itself while driving. If you notice these signs, there is a huge chance you have a bad throttle position sensor in place.  If this is the case, the throttle position sensor will send a false signal, and your car ECU cannot direct the engine to work properly.

3. Engine Rough Idling,  Engine stalling, or idles too slowly

You might wonder if a ‘bad throttle position sensor causes misfire’. If you notice engine misfire, stalling, or rough idling on parked or when you stopped, it could be a clear sign that your throttle position sensor is long gone. When you start your vehicle and allow it to run on idle, the RPM should be around 600-900 RPM.

If your RPM goes above or below that range on idle, that shows you have erratic or rough idling problems. “This can be traced down to a bad throttle position sensor if it happens along with one or more symptoms on the list”.

4. Excess gas consumption

Since the throttle position sensor plays a significant role in proper air/fuel mixture for the combustion process, a false signal as a result of a lousy TPS will cause excess gas to inject into the cylinders and cause Lean/rich fuel mixture issues and poor fuel economy.

Other related sensor partners rely on accurate signals from the throttle position sensor. Suppose it fails, those sensors will send too little or too much airflow resulting in excess gas consumption. Remember, when you experience excess gas consumption, always check your vehicle 02 sensor as well; it plays a vital role in gas mileage.

5. Automatic transmission problems

You might ask, ‘can throttle position sensor affect transmission shifting?’ of course, yes. The throttle position sensor monitors the acceleration position in an engine controlled by the gas pedal located far-right floor on the driver’s side. The throttle position sensor is used to control the amount of gas that goes into the engine and thereby determine engine load and control vehicle speed. If it fails, it can result in automatic transmission hard-shifting issues.

6. Car Accelerates fine but won’t shift up or exceed a certain low speed

This is typically a common TPS failure issue which shows that it’s not allowing adequate power requested by the gas pedal. In such a case, your vehicle will idle and accelerate nice and smoothly but won’t exceed a certain low-speed of 25-35 MPH.

How do you diagnose a throttle body?

If you’re having a problem with your vehicle and notice that you have poor acceleration, or maybe it just seems a little bit doggy. It doesn’t want to go when you push the acceleration pedal or when your engine is idling, and you happen to notice that your RPM or the engine speed goes up and down, kind of erratic idling; you probably have a lousy throttle body. I’m going to show you how to diagnose and fix a car or truck throttle body.

bad throttle position sensor cause misfire

Locate the throttle body: The first thing you want to do to start the diagnose is to find the throttle body. That said, you have to follow the air filter along the air duct straight to the engine. The throttle body is usually located at the part close to the air intake. As you can tell, not all vehicles are the same. In older vehicles, the throttle bodies are typically integrated with the carburetor.

Remove components blocking access to the throttle body: Remove the air intake duct by loosening the fasteners with a screwdriver and take it out of the way. Then, loosen other components blocking access to the throttle body.

Visually inspect the throttle body: Visually inspect the throttle body by looking out for any dark areas that may look like they have some carbon or debris of any sort. Anything like that could cause the butterfly flap inside the throttle body to restrict somehow, which of course, will cause delayed acceleration when you push down the gas pedal.

Inspect the electrical connectors: Unplug the electrical connectors and inspect inside for corrosion of any sort. Any corrosion between the electrical connectors could cause resistance, and of course, that can cause an issue.

Remove the throttle body from the vehicle: Remove the throttle body from the vehicle: Take the correct socket set and ratchet handle from your mechanic tools box and loosen the bolts holding them.

Clean the Throttle Body: Depending on how clogged the throttle body is, by merely looking at the front, you might think it’s not really in the worst condition, but the flip side might say otherwise. You have to clean all the horrible spots inside. When cleaning a throttle body, don’t use any multi-purpose solvent. You have to make sure you specifically get a throttle body cleaner or make sure it’s written carb and choke. Spray the cleaner inside the throttle body and clean off the dead spot with a light washing brush.

Reinstall The Throttle Body:  Coat the throttle body surface with a slight sealant and fix it back. Tighten the bolts that hold it in place and fix everything you remove early. For visual clarification, watch this video.

How to replace throttle position sensor and replacement cost

A vehicle engine needs a predetermined amount of air, just like it needs a predetermined amount of gas. If it doesn’t receive the amount of air necessary for a given moment, it will negatively affect the combustion process. This means lack of engine power and other potential problems. You don’t need to ignore the root of this problem. You need to diagnose the cause of this issue with an automotive scan tool or take your vehicle to your mechanic for a proper check.

how to fix throttle position sensor

If the culprit is proved to be a bad TPS, you have to replace it with a high-end sensor. The average cost for a throttle position sensor is estimated to be $89 – $170. The service fee should be $40 – $60, while the parts should be around $49 – $110. However, this is an estimated price and may slightly go above or less our estimation. You can save the service charge by replacing the parts yourself. The replacement process is pretty easy and straightforward.  If you diagnose your vehicle and find any of these error codes, P0120, P0121, P0122, P0123, P0124, P2135,  it means the ECU has detected an issue with TPS. Stay tuned; let me show you how to replace the throttle position sensor.

Things Needed:

  • Flathead screwdriver
  • 100 mm socket (optional)
  • Ratchet handle
  • Throttle position sensor

Disconnect your negative battery terminal and locate the sensor: You need to disconnect the negative battery terminal to prevent any short circuit or to create a fault code to your car computer. Then, locate the TPS; it’s typically mounted on the throttle body.

Remove the Electrical connectors and unscrew the TPS: Gently remove the electrical connectors on the sensor. This electrical connector is pretty easy to remove. You can easily remove it by pressing the tab on it and wiggle it right off. Once you take off the electrical connector, look for fastening bolts or screws holding the TPS, gently loosen and take it off. Remember, always compare old parts and new parts before installation.

Install the new throttle position sensor: After comparing and confirming that both parts are the same, you need to install the new sensor following the reverse process, starting by mounting the TPS and installing the electrical connector. Whenever you removed an electrical connector like the TPS connector, always inspect the connectors for corrosion. Any corrosion between the connectors could cause resistance, and of course, that can cause an issue. Snap the electrical connector in place, and you should hear a distinct clip sound.

Connect the negative battery terminal and cross-check your work: Head on to the battery and ensure the negative terminals are well tightened. Tighten any other components you removed, start the vehicle, and run on idle and acceleration and see if your effort has finally paid off. Depending on your vehicle, like old Ford rangers and Chevrolet Silverado, Tahoe, and Silverado, you may need to adjust the sensor manually. Most Japanese cars automatically adjust to provide peak performance. Watch this video for visual clarification.

FAQs:

How do you test a throttle position sensor?

There are three electrical connectors on the sensor, the ground wire, the variable output, and the +12 volt input. Disconnect the TPS and insert the alligator test lead on the right Jack on the meter. Turn the range switch to 20k ohm scale or 20,000 ohms. Connect the test leads to variable output, TPS ground wire, and the other lead to the +12 bolts.

Now you want to slowly move the butterfly flap in the throttle body from its close range to the full open range while watching the readings on the meter. The reading should move steadily as you move the flap to the open range and decrease steadily as you return it. Any sudden decrease or increase on the readout signifies a lousy TPS and should be replaced.

How do you reset a throttle position sensor?

The easiest and straightforward way of resetting the throttle position sensor is by unplugging the engine control fuse for 5 minutes or removing the negative battery terminal.

Can a throttle position sensor cause transmission problems?

The throttle position sensor monitors the throttle position that is manually controlled by the acceleration pedal. The acceleration pedal is used to determine engine load, and if it fails, it can lead to hard shifting automatic transmission.

How do you know if your throttle body needs cleaning?

The throttle body is a vital system component of your vehicle fuel management. Most issues associated with the throttle body usually need cleaning. And these issues are caused as a result of carbon buildups that require cleaning. If you notice slowed acceleration or stuttering engine, shaky feeling while driving or uneven acceleration, accompanied by an engine warning light, you need to inspect and clean the throttle body.

Should I clean or replace the throttle body?

Generally, throttle bodies need to be cleaned and not replaced entirely. However, you may need to replace specific related system components. Whenever you notice erratic idling, engine hesitation, or any related sign of a lousy throttle body, always inspect the MAF sensor to ensure it’s working correctly, as it could be the root cause of erratic idling and engine hesitation.

Final word.

Whether you followed these replacement procedures or you called for professional assistance, watching out for the listed symptoms of a bad throttle position sensor will save you from expensive replacement cost, poor fuel economy, weak acceleration, and erratic idling. Always Inspect your throttle position sensor whenever you notice two or more of these signs at a time.

Osuagwu Solomon

Osuagwu Solomon is a seasoned automotive technician for the past 9 years, and a technical writer. He loves writing about auto professional repair guides, DIY repair guides, and buyer’s guide. After spending six years in the automotive workshop, he decided to impact his knowledge to people aside his domain, and he has achieved this by centering his Automotive writing skills on REPAIRS.

Recent Posts