How To Test a TPS Sensor


Cars are great to have until something goes wrong. One of the problems a car can have is that it isn’t idling correctly. It may be fluctuating or high idle but all you know is it doesn’t sound right. It is time for you to test your throttle position sensor (TPS). 

You will need a multimeter to test the TPS sensor. Testing it involves grounding the connectors’ terminals as you put the multimeter probe on black to negative and red to positive. Make sure the throttle is fully closed by turning the key without starting the vehicle. Then read the voltage.

The TPS voltage should be between .2 and 1.5 volts. It should increase to 5 volts when you open the throttle plate. The TPS needs replacing if it doesn’t reach 5 volts.

Read on to find out everything you need to know about the TPS sensor, how to know it’s going bad and more details on how to test it. 

What is a TPS Sensor?

This sensor monitors the engine’s air intake. Air intake is needed for an engine to work properly because air is combined with gas intake and fire to create combustion. When you press the gas, you open the throttle to allow air to pass through, allowing for more gas, and ultimately that gives your car more horsepower. 

The TPS sensor is found on the butterfly spindle or shaft on the throttle body. This is where it monitors the throttle position. The throttle position is important because it rotates as the butterfly opens and closes for air to pass.

What Are the Symptoms of a Bad Sensor?

Your car has its own way of telling you that something is wrong. Some of the ways it tells you the TPS may be going bad is if it lacks power in acceleration, accelerates itself, or won’t shift up to a higher speed. It just won’t go any faster than a low speed.

A clear signal you have a bad TPS is idling problems. Idling problems could include that it doesn’t have a smooth idle. It may idle slowly or even stall. The check engine light may come on.

Your car may send the code P0122. This code happens with your Engine Control Module (ECM) senses something is going wrong with your TPS. That happens when circuit A reports an output voltage that is below the proper voltage. 

Read: Bad TPS Sensor Symptoms

What Is Happening to the Engine?

As stated, your car needs air to combine with the gas and sparks to create combustion that makes it run. The TPS helps monitor the air so when it is faulty, the throttle body controlling the airflow doesn’t work well. 

It might stay shut, preventing airflow at all or won’t close. Failing to close is a troublesome problem because then your vehicle gets too much air which is why it idles high and may suddenly accelerate without you doing anything. 

This is why it isn’t advised to drive with a faulty TPS. Driving with a TPS that is going out is dangerous because your vehicle may not accelerate properly or may accelerate on its own. 

What Do I Need to Know About Testing a TPS?

Testing the TPS on your car is pretty simple if you have a multimeter. Here are the steps onhow to test TPS sensor.

  1. Find the throttle body. It will be the housing attached to the engine block. It will have the fuel line running from it. You will see a device connected to the throttle body that has wires running to the ECU. This is the throttle position sensor.
  2. Now that you’ve identified the parts, you need to find the power, ground, and signal wires. This is simply because all cars use the same colors. Black wires are the ground and red is the power. The signal wire will be another color, like green, yellow or blue.
  3. Turn the multimeter dial to register volts.
  4. You will need to check the reference voltage. This is voltage flowing between the TPS and the ECU. To check it, touch the negative multimeter probe to the negative wire TPS tab and the positive problem to the positive tab. You should see around 5 volts on the multimeter if everything is working.
  5. Now, you should check the signal voltage. To do that, the positive probe goes to the signal wire tab and the ground probe should touch the car frame. A good voltage is 1/2 of a volt. 

How Much Does It Cost to Fix a TPS?

The cost of replacing a bad TPS largely depends on the car model and what the mechanic charges for labor. Generally, Ford vehicles are going to be on the low end of the cost scale while designer brands like German cars are going to cost more.

The median cost of replacing this part runs between $110 and $200. The part itself is pretty inexpensive, costing between $75 to $105, with labor priced somewhere between $35 to $95 

The only option for a bad TPS is a replacement. It can’t be repaired nor would it be worth trying.

Can You Reset a TPS Position?

Yes, you can reset the TPS using the TPMS reset button. This is a button located beneath the steering wheel in most car models 

Here is how you reset the position of a TPS:

  1. Turn the key to the on position without starting the vehicle.
  2. Press the TPMS buttondown until the tire pressure light blinks three times. Then let go.
  3. Start the car. You will need to wait around 20 minutes for the sensor to reset.

Will Cleaning My TPS Help Keep It Working?

Cleaning a TPS won’t fix a problem already occurring but it won’t hurt. It could extend the life of the part over time. All you need to properly clean the sensor si a throttle body cleaner that you can buy at an auto parts store and a towel. 

Just be sure not to overdo it on the cleaner. You just need enough to get the TPS clean. Use the towel to remove grime on the TPS or around it.

How Long Does a TPS Last?

These sensors have an incredibly long lifespan. Most will last to 80,000 miles and beyond. Some will last the entire life of the car.

If you suspect you have a bad TPS and the multimeter test shows it could be bad, take your car to a mechanic and tell him the results of your multimeter test. Your mechanic will do an electrical test too to double-check your results before replacing the part.

Can I Drive Without a TPS?

Yes, you can take the TPS out and drive the vehicle but it won’t drive well. the purpose of the TPS is to tell the ECI when the throttle is open so the car knows how much fuel you’ll need 

When you don’t have a TPS, the ECO will see something that isn’t working with the throttle and airflow and will try to compensate.

You won’t be able to go fast without a TPS in the vehicle and the extreme downside is driving without a TPS will burn up your catalytic converter within a few hundred miles. Catalytic converters can be expensive to replace so it would be best to go ahead and just replace the TPS rather than try to skimp by. 

Can I Replace a TPS Myself?

That depends on how comfortable you are in dealing with mechanical work, whether you have the tools and how well you can follow instructions.

Replacement of a TPS isn’t a major challenge. First, you have to disconnect the negative battery cable and then remove the sensor electrical connector. 

There are mounting screws around the sensor and those will need to come out. 

After that, you just remove the sensor, install the new sensor, and put everything back together. You will need a screwdriver, some pliers, and some towels to clean up.


Paying attention to symptoms occurring in your vehicle will help you find a problematic TPS before it gets to be a serious issue. Replacement is a simple, inexpensive process so there is no reason to try to drive with a faulty TPS. 

Driving with a bad TPS is highly dangerous. It is to your advantage to know how to check it yourself so you can determine if you should take your vehicle to a mechanic. Knowing whether your TPS is bad will also help your mechanic dive into the problem rather than run a lot of expensive diagnostics.

Leave a Comment