How Do You Know If a Throttle Position Sensor Is Bad?

Updated on January 24, 2019
Throttle position sensor (right hand side device).
Throttle position sensor (right hand side device). | Source

Yes. How do you know if a throttle position sensor (TPS) is bad? Of course, some symptoms can tell you when a TPS may be bad. But these symptoms may come from other bad sensors, parts, or components. So you need to conduct some tests.

The TPS connects to the throttle plate on the throttle body. The position sensor has a variable resistance potentiometer (or contact points, depending on model) that sends a varying voltage signal to the Power Control Module (PCM, your car's engine computer) according to the position of the throttle plate.

This plate rotates when you depress the gas pedal to allow more air to enter the intake manifold. With the engine running, the position of the throttle plate (along with other sensors) tells the computer how much fuel the engine needs at any given moment.

So, without the correct signal coming from the TPS, you begin to notice drivability problems. Fortunately, it's not that hard to test the sensor. You can use the position sensor operating characteristics to test it using a digital multimeter (DMM).

If you haven't used a multimeter before, just take a look at the next video. In a couple of minutes you'll be ready to test the throttle position sensor in your car. And if you're looking for an inexpensive but good DMM for your toolbox—you need to use one for many DIY car projects—you can find one at your local auto parts store or online.

The most typical failure you'll find on a TPS is wear, a short or an open on the circuit of the contacts or variable resistor. This guide will help you test the throttle position sensor in a few minutes and know whether you need to replace it.

Index

I. How to Test a Throttle Position Sensor

A. Is Your TPS Connected to Ground?

B. Is Your TPS Connected to Reference Voltage?

C. Is Your TPS Producing the Correct Signal Voltage?

WARNING - Using a DMM

II. Throttle Position Sensor Adjustment

Bad TPS Symptoms
Lean and Rich fuel condition problems
Bad computer signals to other actuators
Ignition timing problems
Triggering of trouble codes (depending on car model)
Rough idle
Hesitation
Stumble
Surging
Stalling
Crank-No start condition

I. How to Test a Throttle Position Sensor

The most common TPS test is to measure for resistance (ohms) or voltage at the various positions, including throttle plate closed, half open and fully open. We'll use voltage to test the TPS here.

1. Open the hood and remove the air cleaner assembly where it connects with the throttle body.

2. Inspect the throttle plate and the walls of the throttle body surrounding the throttle plate.

* If you see carbon buildup around the walls and under the throttle plate, spray some carburetor cleaner on a clean shop rag and wipe the buildup with it until the surface is completely clean. Carbon buildup can prevent the throttle plate from closing properly and moving freely.

3. Locate the TPS mounted on the side of the throttle body. The TPS is a small plastic block with a three wire connector.

Source

A. Is Your TPS Connected to Ground?

1. Carefully unplug the electrical connector from the TPS.

2. Examine the electrical connector wires and terminals for dirt, contamination and damage.

3. Now, set your DMM to a suitable setting, like 20 Volts, on the DC voltage scale.

4. Turn the ignition key to the ON position, but don't start the engine.

5. Connect the red test lead from your DMM to the battery positive post, the one marked with a "+" sign.

6. And touch the black test lead from your DMM to each of the three electrical terminals of the TPS electrical connector.

* The one terminal that reads 12 Volts on your DMM is the ground terminal. Make a note of the color of this wire.

* If none of the terminals reads 12 Volts, there's a problem in that part of the wiring leading to the TPS you need to fix because the TPS has no ground.

7. Turn the ignition key OFF.

Locate the TPS to the side of the throttle body.
Locate the TPS to the side of the throttle body. | Source

B. Is Your TPS Connected to Reference Voltage?

1. Now connect the black test lead from your DMM to the ground terminal on the TPS connector you just identified.

2. Turn the ignition key to the ON position, but don't start the engine.

3. Connect the red test lead to each of the other two terminals.

4. One of the terminals should read 5 volts, or pretty close to it. That terminal is providing the reference voltage to the TPS to produce the voltage signal. Make a note of the color of the wire connected to this terminal. The third wire corresponds to the signal voltage or signal wire.

* If you don't get 5 volts from any of the two terminals, there's a problem in the circuit you need to fix because there's no reference voltage going to the TPS. Check the circuit for bad terminals, loose, dirty or damage wires.

5. Turn the ignition key OFF.

6. Plug back in the electrical connector to the TPS.


C. Is Your TPS Producing the Correct Signal Voltage?

1. Now backprobe the signal and ground terminals on the TPS electrical connector. If necessary, use a couple of pins to backprobe the wires.

2. Connect the positive (red) test lead from your DMM to the signal wire and the black negative (black) test lead from your DMM to the ground wire.

3. Turn the ignition key ON but don't start the engine.

4. Make sure the throttle plate is fully closed.

5. Your DMM should read around 0.2 up to 1.5 Volts or close to it, depending on your particular model. If the readout on your meters shows only a zero, make sure you're at a low setting—usually at the 10 or 20 Volts setting. If your meter still reads zero, continue with this test anyway.

6. While watching the readout on your DMM, gradually open the throttle plate until is fully opened (or have an assistant gradually depress the gas pedal to the floor).

* Your DMM should read 5 volts or close to it when the throttle plate is fully opened.

* Also, make sure that the voltage increases smoothly as you gradually open the throttle plate.

* If you notice the voltage skipping or stuck at a certain voltage value, as you gradually open the throttle plate, your TPS is not working properly and you need to replace it.

* Also, if your TPS doesn't reach 5 volts, or close to it (up to 3.5V on some models), when the throttle plate is fully opened, replace the TPS.

7. Repeat step 6, only this time use the handle of a screwdriver to lightly tap on the position sensor as you open and close the throttle plate. If the voltage skips as you tap the sensor, replace it.

8. Turn OFF the ignition key and remove the pins.

If your have an adjustable throttle position sensor (old vehicle model), and your readings are out of specification, try to adjust the sensor first before replacing it. Your sensor is adjustable if you can loosen the sensor mounting bolts and rotate the sensor left or right. If necessary, head over to the next section Throttle Position Sensor Adjustment.

WARNING - Using a DMM

When testing electronic devices in your car, use a 10-megaohm impedance digital multimeter to protect sensitive electronic devices in your vehicle.

II. Throttle Position Sensor Adjustment

This is an example of an adjustment on an externally mounted TPS. Other models with different configurations require a variation of the following steps. But this will give you a general idea of the adjustment procedure.

1. Loosen the sensor mounting bolts just enough so that you can rotate it by lightly tapping on it with a screwdriver handle.

2. Backprobe the position sensor to monitor the voltage signal with your DMM.

3. Turn the ignition key to the ON position but don't start the engine.

4. Keep the throttle plate at the close position (or at the position specified in your repair or service manual).

5. Verify that the voltage corresponds to the specified in your manual. If not, rotate the sensor left or right until you obtain the specified voltage.

6. Then, hold the TPS in that position and tighten up the mounting screws.

If the TPS is unable to reach the specified voltage, replace it.

NOTE: On some models, you need a feeler gauge to adjust the position sensor. Also, you may need to adjust a stop screw in the throttle body and, still in some other models, adjust a dash pot that prevents the throttle plates from suddenly closing. For this, read the instructions in the repair manual for your specific vehicle make and model.

Knowing how to test a throttle position sensor can save you time, and, most importantly, prevent you from changing parts unnecessarily. So this simple test can help you get your car back on the road faster. And the test is not difficult. You can do it at home in just a few minutes.

This article is accurate and true to the best of the author’s knowledge. Content is for informational or entertainment purposes only and does not substitute for personal counsel or professional advice in business, financial, legal, or technical matters.

Questions & Answers

  • What does it mean if my throttle goes straight to 5v before you move the throttle?

    The resistance is probably bad.

  • Hi. I have a 2008 Ford Focus, 1.4L. The EML and red cog on dash indicate throttle positioning sensor. I have changed the throttle body and the entire accelerator pedal (sensor included) and the issue is still there. The car will drive perfectly normal until the red cog light appears on the dashboard. There is then a loss of power and there is a delay between pushing the accelerator and the car accelerating. What could be the problem? Please help!

    The red cog usually comes on because of a fault with the glow plugs or the relay. But it's better to have it diagnosed. There could also be a problem in the powertrain.

  • If I throttle my car, it takes too long to decrease the acceleration. Is it from the TP sensor? The check engine light is also on.

    Not necessarily. Pull down the codes and see what the computer is pointing at as the fault. There might be another sensor not responding quite right.

  • I have an 03, Z71. The TPS and throttle body are one piece. Codes read the TPS was bad, so I replaced the throttle body. Codes still say throttle body is bad. Do you have any thoughts?

    You need to check the reference signal to the sensor and what the sensor is reporting to the computer. It could be a problem in the circuit or the connector. You can use a DMM for this. Use your vehicle repair manual to check or identify the wires, if necessary.

  • My throttle position sensor is not getting ground. What do I do?

    Check along the wire, from the sensor to the computer, that provides ground to the sensor. Make sure the wire is not damaged, or loose in the harness. Use a test light. If the wire is OK, the problem could be on the computer itself. In this case, it is better to fix the ground on the computer. Trying to run a new ground to the sensor may create other issues.

Comments

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    • profile image

      Marquet 

      6 weeks ago

      Very good reading, thank you.

    • profile image

      JOHN 

      6 weeks ago

      thank you for this site my cagive TL1000 as a bad problem back fireing in number two port tring to set the TP. bY f1 on the dash dose not work bike starts ok.in be tween 1200rpm to 2000rpm it spits in number 2 port

      i try hand your methed. i no there 4.5v on full throttle will do the pin test

      not cheap to replays. 23102019

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      8 weeks ago

      There could be several reasons why it is misfiring. Usually, this is due to a fault in the fuel or ignition system. Download the trouble codes, they can help a lot when diagnosing the problem. Your diagnostic strategy depends whether it is misfiring on the same cylinder(s) all the time -- concentrate on those cylinder. If it may fire on any cylinder, then check the system. But it can also misfire randomly. These other posts may help:

      https://axleaddict.com/auto-repair/Engine-Misfires...

      https://axleaddict.com/auto-repair/P0300-Random-Mi...

      Hope this helps.

    • profile image

      Arthur Sibande 

      8 weeks ago

      2010 kia picanto, it was misfiring then i overhauled it, after i drove for 50km then it started misfiring again, i had to change fuel filter and pump but still, now it wont start. What might be the problem?

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      2 months ago

      Check the TPS with a digital multimeter. You should see a smooth increase and decrease in voltage as you operate the throttle plate. If voltage jumps or skips, then you got a bad TPS.

    • profile image

      wasim 

      2 months ago

      Throttle position showing on scanner seems more and fluctuate more between 50% to 25% sometimes 100%.

      On starting the engine in morning, engine misfires then its stable but even on 6oorpm idle, the TP on scanner is showing 40% 50% which i think is not correct.

      rpm flutaute more at low speeds or 1st or 2nd gear then stables.

      Any idea whats wrong ?

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      2 months ago

      Hard to say what's wrong with it, but from your description it seems like a sensor problem. Check for trouble codes, even if the check engine light is not on. You may find a pending trouble code. Check the mass air flow sensor, it may be bad or dirty ( a common source of problems like this). This other post may help:

      https://axleaddict.com/auto-repair/How-to-Test-a-M...

      The problem can be in the ignition system as well. Make sure you got good spark on all cylinders. If you get a misfire in one cylinder in particular, check the injector and ignition for that cylinder. If misfire happens randomly, this other post may help:

      https://axleaddict.com/auto-repair/P0300-Random-Mi...

    • profile image

      Hasham 

      2 months ago

      Hy,Dan ferrell

      I have a 1995 honda civic swaped 98 honda civic engine D15z

      Laterly, my car has a problem of flactuating idle from 600 to 900 and also continues when stop on a stop signal but after consulting the mechanic

      I have an issue of bad idle and a misfire little sounds like (dup dup ) can cause rpm down to 700 then 500 and stays at 500 and a misfire will be same at interval and gone when revs up , when just drive a car feels hesitation and a huge vibration while releasing the clutch to drive the car recently i will shows this problem to the mechanic and spent a lot of money in it but nothing would be solved the mechanic clean the throttle body, IAC valve and also check the wiring harness ,change the head gasket but nothing would worked please help

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      3 months ago

      You need to check the throttle body and accelerator pedal sensor. It might not be sending or receiving the signal.

    • profile image

      Allen Fuller 

      4 months ago

      I have a 2003 VW Golf. ECP light came on acceleration failed. I cleaned the throttle body and the car idles well. But very little happens when I push the accelerator. No revs just stays the same idle speed.

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      5 months ago

      This could be a faulty TPS (throttle position sensor) with a dead spot. At idle, have the transmission at Park or Neutral, set the parking brake and increase engine speed to 2500-2800 rpm. If you can replicate the misfire, it might be this sensor. Have it checked:

      https://axleaddict.com/auto-repair/How-Do-You-Know...

      Sometimes, a sensor causing a misfire will trigger a check engine light. Download trouble codes even if the engine light is not on, and see if you get any pending codes that can guide you here.

      If the engine seems to lose power after reaching the 2500-2800 rpm point, this can also be a clogging fuel filter. Hope this helps.

    • profile image

      Margus 

      5 months ago

      My Audi have misfire about 2500-2800rpm,usual rpm at 50- and 90km/h.

      Accelerate good but something hold back at specific rpm.

      Suggestions please.

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      6 months ago

      It's possible, but it's not the only one that may cause this symptom. You may want to check for trouble codes. Most auto parts stores will download the codes for you, if you don't have the scanner. And before replacing a sensor have it check first.

    • profile image

      Kathy Holmgren 

      6 months ago

      Have a 2007 Honda CR-V. Having trouble starting car. Engine turns over on first 2 tries. On 3rd try, when I give it gas, it starts. Someone told me it may be my throttle position sensor???

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      6 months ago

      You may need to calibrate the unit. This youtube video might help:

      https://www.youtube.com/watch?v=o9DYIb6ZwPg

    • profile image

      Raja 

      6 months ago

      I just replaced a tps in my honda crv 1st gen, it doesnt seem to want to budge very much and it only reads .01, any suggestions?

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      8 months ago

      You may have a vacuum leak; this other post may help:

      https://axleaddict.com/auto-repair/How-to-Find-and...

      Also, take a look at this post, if necessary:

      https://axleaddict.com/auto-repair/What-Causes-Low...

    • profile image

      zeray 

      8 months ago

      the same problems on the above I have toyota model LAN25l

      during driving the fuel accelerator pedal work but she cant increase speed or power not good and at the exhaust excess gas shown so what shall i do help me please

    • profile image

      Leonard Chinguri 

      9 months ago

      Best

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      9 months ago

      Glad it helped.

    • profile image

      Adrian 

      9 months ago

      I wish i would have found this page when i began dealing with this problem. The step by step and detailed instruction was very helpful and easy to understand and follow.

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      9 months ago

      Since you just replaced the throttle body, make sure all the electrical connections to the throttle are tight and clean - slightly pull on the wires to check that they are not loose. Also, check the engine ground connections. These are the most common problems. The throttle body valve (the center plate on the throttle) should have a small opening (just a crack) that you can barely see; push on the valve and you'll feel the opening. This is a spring loaded mechanism. This small opening is an adjustment to compensate for different temperatures - If this play is not there, you need to adjust the valve. Usually you can remove the valve-plate, tighten the bolts with the valve perfectly close. Once tighten, the plate should open itself just a crack. Hope this helps.

    • profile image

      Melinda 

      9 months ago

      I have 2007 Tahoe. I changed the whole throttle body on Friday because I was getting the reduced engine power message. It worked fine at first. Now I can crank my Tahoe and it might come on but once I kill it for 60 seconds or so and crank it back up the message goes away. It has done this several times over the weekend. Any suggestions on what is causing this?

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      10 months ago

      You need to make sure that it does have good spark and fuel pressure is right. Also, this could be a sensor (crankshaft position sensor or camshaft position sensor) problem. Download trouble codes from the computer memory and see if you find anything. That could you time.

      This other post may help as well:

      https://axleaddict.com/auto-repair/Why-My-Car-Stal...

    • profile image

      Mdeva 

      10 months ago

      Hello, I am driving a polo 6r 1.4 2010 clp engine, it cranks and starts after a while but I have to put the foot on the gas pedal, and then it does not idle

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      10 months ago

      I was thinking along the lines of a bad ground, and found this forum with a problem similar to yours. But, if the needles move with the key On, this could be also related to the ignition switch. Hope this helps:

      https://www.thetruckersreport.com/truckingindustry...

    • profile image

      Roberrto 

      10 months ago

      Got a 1998 peterbilt with detroit 60 , speedo and tach gauge quit working when i turn the key on the needles would move. any help would be greatly apreciated

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      12 months ago

      I’m not familiar with this type of vehicle but you may want to check the CDI module or possibly a coil that has broken. This symptom is similar to a car ignition system. When a coil breaks, heat causes the coil to expand and cuts off current, causing the engine to shut off. Hope this helps.

    • profile image

      delbert ragels 

      12 months ago

      2008 Suzuki quad model lt-a750x dies and will not start after 15 minutes of riding will not start until it sets for a few hours

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      13 months ago

      Physically, common signs of a bad distributor cap are carbon traces and cracks.

      As for symptoms, your may notice hard to start, misfires and other common ignition systems issues.

    • profile image

      Jethro 

      13 months ago

      Hi

      how do you notice the failure of the distributor cap ?

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      14 months ago

      Hi Khalil,

      This post might help you:

      https://axleaddict.com/auto-repair/Why-My-Car-Stal...

      Good luck

    • profile image

      Khalil ur Rehman 

      14 months ago

      Sir I have Toyota Yairs 2005 my car is not idling when i start it it stalls after a few seconds, i have checked MAF, TPS manifold fuel pressure every thing is fine please guide me what to do and what not to do in this case i am very thankful to you in this regard.

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      18 months ago

      Hi John,

      Make sure you are probing the right terminals - also, you can try checking resistance to confirm your readings.

      Good luck

    • profile image

      John a 

      18 months ago

      What happens if it reach a higher volt count than 5.

    • profile image

      Nitra coleman 

      20 months ago

      Have y’all had a problem like this before ?

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      20 months ago

      Hi NC,

      Follow the instructions in the post to test your TPS. Make sure to get the trouble codes from the computer. Other faulty sensors can cause the same symptoms: a bad O2s, temperature sensor and intermittent electrical problems.

      Good luck

    • profile image

      Nitra coleman 

      20 months ago

      How do you know if you have a bad tps I replaced it but every since then it have been jerking and will not go pass 2500rpm

    • profile image

      zelo 

      24 months ago

      oh man just what i needed. I am not a mechanic, but currently cannot afford one. I am not a novice diy, a litter better, but its a cadillac soo...jeez

    • Dan Ferrell profile imageAUTHOR

      Dan Ferrell 

      2 years ago

      Fixed

      Thanks a lot JG

    • profile image

      J Gesink 

      2 years ago

      My complements on this set of instructions, great job! And, I think there is a minor error in part C., Step 7 where it states: " 7. Repeat step 21, only this time use the handle ...."

      I think it should state "Repeat step 6" rather than "Repeat step 21"

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