How to Test Throttle Position Sensor and What to Do If It Goes Bad

The throttle position sensor, otherwise known as TPS is mounted on the Throttle Body of every vehicle.

The throttle position sensor is meant to function for a lifetime.

So, it doesn’t need to be changed for a lifetime unless your luck is bad.

The average lifetime of a car or other vehicles is 2,00000 miles.

After driving 50K/100K miles, some symptoms may indicate your TPS sensor is not functioning properly.

Then you have to clean and re-install the TPS sensor, or you have to replace it.

Before cleaning or replacing, you must test the TPS sensor’s functionality.

Today, we will learn how to test the throttle position sensor and what happens when a TPS sensor goes bad.

Let’s begin.

How to Test Throttle Position Sensor with Multimeter [6 Steps]

how to test throttle position sensor

A throttle position sensor controls how much air should enter the engine to maintain the air-fuel mixture.

A faulty throttle position system can’t supply the right amount of air to the engine.

Instead, it supplies more or less air to the engine than standard.

So, the TPS must be in good condition to maintain the right air-fuel mixture.

Otherwise, the airflow process will be hampered.

To know whether the throttle position sensor of your vehicle is good or bad, you need to test it.

To perform the test, you’re going to need-

  • Digital meter (set it on a DC voltage range)
  • A couple of jumper wires
  • A straight pin or a sewing needle

You can test the throttle position sensor of your vehicle by following 6 steps.

Step 01

how to test throttle position sensor

Locate the throttle body and find out the throttle position sensor.

You will find the sensor on the side of the throttle body.

A TPS has three wires connecting the sensor with the ECU.

Step 02

Now identify the power, ground, and signal wires of the throttle position sensor.

Note that, Black wire indicates ground, and red indicates the power.

The color of signal wires varies from vehicle to vehicle or model to model, and they are available in green, yellow or blue.

Step 03

how to test throttle position sensor

Set the Digital or multimeter to DC volts.

Take the black probe of the digital meter and connect it to the negative battery.

You can also use the engine ground instead of the negative battery.

Now you can take the other jumper wire and connect it to the positive red wire of the meter.

You can use a needle to connect them.

Step 04

Pull the boot down to expose the wires of the throttle position sensor.

After pulling down the boot, you can easily reach into the connector wires.

Put the engine to be on a position.

Step 05

Test the power supply of the TPS sensor using the digital meter.

The top wire should give a 5-volt reading, whereas the center or ground wire will not give any reading.

Step 06

Now, check the signal wire.

To check it, connect the positive probe to the signal wire tab.

Its voltage should be around 0.5 volt DC without the gas pedal being depressed.

The voltage will increase proportionally as the gas pedal is depressed.

It should be increased to around 5 volts of DC.

If the signal output matches this voltage, the throttle body position sensor is good; if it doesn’t, it isn’t faulty and needs to be changed.

This video clearly shows how to test a throttle position sensor with a multimeter.

What Happens When a TPS Goes Bad in Duramax?

There are some common problems when the throttle position sensor goes bad.

Let’s discuss the 06 most common problems that indicate the throttle position sensor is faulty or in bad condition.

Problem 01: Acceleration Problem

A bad or faulty throttle position sensor causes acceleration problems.

When the TPS goes bad, there will be a noticeable increase or decrease in acceleration.

Unusual acceleration hampers the driving ability and experience of your vehicle.

Acceleration problem is the most common symptom of a bad TPS.

Problem 02: “Check Engine” Warning Light Pops Up

If the throttle position sensor goes bad, it fails to monitor the throttle valve.

As a result, it fails to control the airflow of the engine.

When the ECU detects this problem, ECU illuminates a Check Engine warning on the driver dashboard.

Sometimes ECU triggers TPS-related trouble codes- P0121, P0122, P0123, P0124, P2135 and P2138, etc.

“Check Engine” warning should not be avoided.

Necessary steps should be taken without delay.

Problem 03: Fuel Economy

A bad TPS fails to control the air-fuel ratio.

As a result, too much or too less airflow happens, and the combustion (where air and fuel burn) gets affected.

It causes increased or decreased fuel economy than standard.

The overall lifespan of the engine is greatly affected negatively by the increased/decreased fuel economy.

The standard lifespan of a car is 350K miles; it may be reduced to 150K/200K miles due to a bad TPS sensor.

Problem 04: Transmission Shifting Problem

ECU controls the transmission shifting/gear shifting.

But to control it, the computer needs to know the exact position of the throttle.

According to the ECU signal, the throttle opens and closes.

A bad throttle position sensor sends wrong information to the ECU, and it causes the throttle to open or close faster or slower than usual.

And it causes gear/transmission shifting issues.

Problem05: Bucking and Jerking

If the TPS goes bad, it distorts the signal sent to the engine.

As a result, the vehicle will be jerking and bucking when you apply and release the gas pedal quickly.

Problem 06: Unsteady Engine Idling

A faulty TPS sensor causes the engine to idle unsteadily.

TPS sensor sends signals to the ECU that tell it how much throttle to apply.

When the TPS fails to send correct signals, the engine will not be able to adjust the throttle properly.

As a result, it causes the engine to idle unsteadily.

What Should I Do If the TPS Sensor Goes Bad?

After testing or observing the throttle position sensor, you will know whether it’s faulty or not.

If the TPS sensor is faulty, then there are 2 solutions.

Solution 01: Re-installing after Cleaning

Check the throttle position sensor.

If the throttle position sensor is showing any symptoms mentioned above, clean it with cleaner air, then re-install the throttle position sensor.

Hopefully, the problem will be solved instantly.

If not, then-

Solution 02: Replacing with a New One

If cleaning doesn’t work, then the throttle position sensor of your vehicle is faulty.

You must change the TPS sensor to a new one.

The price range of the throttle position sensor is between $60 to $180.

Keep in mind that before replacing testing the throttle position sensor is a must.

Final Thoughts

Now you know what happens if your TPS goes bad and how to test the throttle position sensor with a multimeter.

After testing, if you find the throttle position sensor is faulty, we suggest replacing the TPS sensor with a new one instead of cleaning or re-installing it.

Cause many of our customers reported, cleaning and re-installing the TPS doesn’t solve the problem entirely.

After driving a few thousand miles, it occurs again.

So, we suggest replacing the throttle position sensor instead of resetting it.

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