How To Test The GM 2.2L Throttle Position Sensor (TPS)

In this article, I'm gonna' show you how to test the throttle position sensor on your 2.2L Chevy Cavalier or 2.2L Pontiac Sunfire. So if the check engine light is on with diagnostic trouble codes: P0121, P0122, P0123 this is the article that is gonna' help you to solve them.

All of the steps of the throttle position sensor test are explained in detail and more importantly, you'll get a detailed interpretation of the possible results you'll obtain on your car.

In Spanish You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS Con Multímetro (GM 2.2L) (at:

NOTE: To see all 2.2L Cavalier and Sunfire Test Articles, go here: GM 2.2L Index Of Articles.

TPS TEST 1: Testing The TPS Signal

Testing The TPS Signal With A Multimeter. How To Test The GM 2.2L Throttle Position Sensor (TPS)

Before you jump into the throttle position test on your Chevy Cavalier or Pontiac Sunfire, read the entire article first. I especially recommend reading the section: How The Throttle Position Sensor Works. Besides, there's a quiz at the end of the article.

Also, depending on the year of your specific 2.2L GM vehicle, the TPS will be one of two designs (see image at the beginning of this tutorial), but they both use the same connector and so the colors (of the wires) will be the same (and more importantly the tests steps are the exact same).

OK, let's jump into this first test. Almost forgot to tell you that you're gonna' need someone to help you complete part of this test. This is what you'll need to do:


  1. 1

    If the engine is cold, crank it up and let it run for about 20 minutes or till it reaches it normal operating temperature. By having a warmed-up engine, the more effective the test will be at finding a failing throttle position sensor (TPS).

  2. 2

    With your multimeter in Volts DC mode and with the throttle position sensor connected to its connector, probe the sensor's dark blue wire. This is the wire that connects to the terminal labeled with the letter C in the illustration above.

  3. 3

    Ground the black multimeter test lead on the battery negative (-) terminal and then have your helper turn the key ON but the engine OFF.

  4. 4

    What your multimeter should read is about 0.5 to 0.7 Volts DC. If it doesn't, don't worry about it just yet, continue with the other steps.


  1. 5

    Now, with everything still connected from test steps 1-4, open the throttle by hand till it reaches its full open position in a slow and deliberate way.

  2. 6

    Your multimeter will register an increasing DC voltage till it stops at about 4.5 to 4.9 Volts DC (once the throttle is fully open).

  3. 7

    Now, slowly close the throttle, while you keep your eyes on the multimeter. Your multimeter should show a decreasing voltage till it reaches the voltage you recorded in step 4.


  1. 8

    Now, you'll need a helper for the next steps:

    Your assistant needs to lightly tap the TP sensor with the butt of a screw-driver's handle (or something similar, and I want to emphasize the words 'lightly tap’) as you open and close the throttle once again.

    What you are trying to confirm is if the tapping of the screw-driver on the TPS will have an effect on the voltage readings on the multimeter. The tapping SHOULD NOT have any effect on the voltage readings.

  2. 9

    Repeat step 8 several times to make sure of your multimeter test results.

Interpreting The Results

CASE 1: The multimeter registered a smooth increase or decrease in voltage. This result lets you know that the throttle position sensor is good and not the cause of the issue.

Now, if the throttle position sensor code keeps coming back, take a look at the heading: TPS Code Will Not Go Away for a few more suggestions as to what could be causing the TPS diagnostic trouble code (DTC).

CASE 2: The multimeter DID NOT register a smooth increase or decrease in voltage and you saw the voltage reading skip or go dead when tapping the TPS. This test result confirms, beyond any doubt, that the throttle position sensor (TPS) is bad. Replace the throttle position sensor.

CASE 3: The multimeter DID NOT register any voltage. This is not good, but does not condemn the TPS as bad yet. Two more things need to be verified first, which are power and Ground to the sensor. Go to: TPS TEST 2: Testing The 5 Volt Reference Signal.