How To Test The Throttle Position Sensor (1998-2003 2.2L S10 and Sonoma)

TEST 2: Verifying Throttle Position Sensor Has Power

If the TPS is NOT creating a voltage signal that increases/decreases as you manually open the throttle plate, the next step is to make sure that it's getting power.

Power comes from your S10 or Sonoma's PCM thru' the gray (GRY) wire of the TPS connector.

This power is in the form of 5 Volts DC and we'll do a simple multimeter voltage test to confirm it.

Alright, here are the test steps:

1. 1

   Set your multimeter to Volts DC mode and turn the key on but don't crank or start the engine.
   
   This will power up the TP sensor's connector.

2. 2

   With the red multimeter test lead probe the GRY wire of the TPS engine wiring harness connector.
   
   IMPORTANT Do not probe the front of the TPS connector. Probing the metal terminal of the TPS connector could damage it and require that you replace the connector. Use a back probe or a wire piercing probe instead of probing the front of the connector.

3. 3

   Connect the black multimeter test lead to a good and clean Ground point on the engine or directly on the negative (-) battery terminal.

4. 4

   When you've set up the test, have a helper turn the Key On Engine Off (KOEO).

5. 5

   Your multimeter should display 4.5 to 5 Volts on its screen. OK, now let's interpret your test results below:

Let's analyze your test result:

CASE 1: The GRY wire is feeding the TPS with 4.5 to 5 Volts. This means that the throttle position sensor (TPS) is getting power from the fuel injection computer.

The next and last test, is to make sure that the throttle position sensor is getting Ground (from the PCM too). For this test, go to: TEST 3: Verifying Throttle Position Sensor Has Ground.

CASE 2: The GRY wire IS NOT feeding the TPS with 4.5 to 5 Volts. Double check all of your connections and repeat the test.

If your multimeter still doesn't register the 4.5 to 5 Volts DC, then this test result tells you that the TPS itself is not at fault (and thus causing the TPS trouble code). Without power, the TPS can't create a throttle angle voltage signal. Although beyond the scope of this tutorial, your next step is to diagnose and restore this missing power.

TEST 3: Verifying Throttle Position Sensor Has Ground

Up till now, your 2.2L S10's (or Sonoma's) TPS diagnostic tests have confirmed:

1. The check engine light is lit up by a TPS trouble code (P0121, P0122, or P0123).
2. The TPS failed TEST 1.
3. The GRY wire of the TPS engine wiring harness connector has power (TEST 2).

For our 3rd and last test, we're going to make sure that the black (BLK) wire of the TPS connector is feeding the TPS with Ground.

To verify the TPS is getting Ground, we're going to do a simple voltage test on the BLK wire with our multimeter.

IMPORTANT: Ground is provided directly by the PCM on your S10 (or Sonoma). Be careful and don't intentionally or accidentally short this wire (circuit) to battery power or you will fry the fuel injection computer. The multimeter voltage test described below is a safe way to check for this Ground.

OK, here are the test steps:

1. 1

   Set your multimeter to Volts DC mode.

2. 2

   Probe the TPS connector's BLK wire with the black multimeter test lead.
   
   IMPORTANT: Avoid probing the front of the TPS connector. Probing the metal terminal of the TPS connector could damage it and require that you replace the connector. Use a back probe or a wire piercing probe instead of probing the front of the connector.

3. 3

   Now, with the red multimeter test lead, probe the battery positive (+) terminal.

4. 4

   Turn the key to its ON position but don't start the engine. This will power up the fuel injection computer.

5. 5

   Your multimeter will display 11 to 12 Volts if the BLK is feeding Ground to the throttle position sensor (TPS).

Let's take a look at what your test results mean:

CASE 1: Your multimeter confirms that the BLK wire is feeding the TPS with Ground. This is the correct and expected test result and confirms the TPS is getting Ground.

Up to this point you have confirmed that:

1. The TP sensor's signal does not increase/decrease as you open/close the throttle plate (TEST 1).
2. The DK BLU wire has 4.5 to 5 Volts and thus the TPS is getting power.
3. In this test, you've have verified the TPS is getting Ground on the BLK.

These 3 test results confirm that the TPS is bad and needs to be replaced.

CASE 2: Your multimeter confirms that the BLK wire IS NOT feeding the TPS Ground. Double check that you're testing the correct TP sensor harness terminal wire and repeat the test.

If your test result still indicates that the TPS is not getting Ground, then we can conclude that one of two things are causing this lack of Ground:

1. There's an open in the BLK wire between the TP sensor harness connector and the fuel injection computer's harness connector.
2. The PCM has an internal problem (although this is extremely rare).

Although testing these two conditions are beyond the scope of this article, you have now eliminated the throttle position sensor (TPS) on your 2.2L S10 (2.2L Sonoma) as being the cause of the problem and/or the TP sensor diagnostic trouble code (DTC) lighting up the check engine light (CEL).

More 2.2L GM Diagnostic Tutorials

You can find a complete list of 2.2L GM tutorials in the following 2 indexes:

• GM 2.2L Index Of Articles.
• GM 2.2L Index Of Articles (at troubleshootmyvehicle.com).

Here's a small sample of the tutorials you'll find in the indexes:

• How To Test The Front Oxygen Sensor With A Multimeter (2.2L GM).
• How To Test The GM 2.2L Throttle Position Sensor (TPS).
• How To Test The GM 2.2L Ignition Coil Pack.
• How To Test The Fuel Injectors With a Multimeter (GM 2.2L) (at: troubleshootmyvehicle.com).