How To Test The Throttle Position Sensor (1991-1993 2.8L Chevy S10 Pickup, GMC Sonoma)

TEST 2: Making Sure Throttle Position Sensor Is Getting Power

If you're performing this test step, your TPS has failed TEST 1 on the previous page.

The next step is to ensure that the TPS is receiving power, which is in the form of 5 Volts DC.

This voltage comes directly from your S10 pickup or Sonoma's fuel injection computer via the terminal of the TPS connector labeled with the letter A (see image above).

If the TPS is receiving power from terminal A, your multimeter should read 4.5 to 5 volts DC.

OK, let's get testing:

1. 1

   Disconnect the TPS from its electrical connector.

2. 2

   Place your multimeter's dial in Volts DC mode.

3. 3

   Turn the key to the RUN position, but don't start the engine.
   
   This will power up the TP sensor's connector.

4. 4

   Connect the black multimeter test lead directly on the negative (-) battery terminal.

5. 5

   Probe terminal A with the red multimeter test lead.
   
   IMPORTANT Be careful when probing the metal terminal of the TPS connector. Damaging the terminal will require that you replace the connector. Use a back probe or a wire piercing probe instead of probing the front of the connector.

6. 6

   Your multimeter should display 4.5 to 5 Volts.

Let's examine your test result:

CASE 1: Terminal A has 4.5 to 5 Volts. So far so good since this tells you 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: Making Sure Throttle Position Sensor Is Getting Ground.

CASE 2: Terminal A DOES NOT have 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: Making Sure Throttle Position Sensor Is Getting Ground

So far, your TPS diagnostic tests have confirmed the following:

• You have a TPS trouble code lighting up the check engine light (CEL).
• The TPS is not creating a decreasing/increasing throttle angle voltage signal (TEST 1).
• The TPS is getting power (TEST 2).

For our final test, we'll make sure the TPS is receiving ground.

The terminal that supplies ground to the TPS is the terminal labeled with the letter B in the image above.

IMPORTANT: Ground is provided directly by your Chevy S10 or Sonoma's fuel injection computer. Be careful and don't intentionally or accidentally short this wire (circuit) to battery power or you'll fry the fuel injection computer.

OK, here are the test steps:

1. 1

   Disconnect the TPS from its electrical connector.

2. 2

   Place your multimeter's dial in Volts DC mode.

3. 3

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

4. 4

   Connect the red multimeter test lead directly on the positive (+) battery terminal.

5. 5

   Probe terminal B with the black multimeter test lead.
   
   IMPORTANT Be careful when probing the metal terminal of the TPS connector. Damaging the terminal will require that you replace the connector. You can use a back probe or a wire piercing probe instead of the multimeter test lead.

6. 6

   Your multimeter should display 10 to 12 Volts.

Let's see what your multimeter test result means:

CASE 1: The multimeter showed 10 to 12 Volts. This test result confirms that the TPS is getting Ground from your S10 pickup or Sonoma's fuel injection computer.

You can conclude the TPS is bad and needs replacement if you have:

• Confirmed the TP sensor is not providing a varying voltage signal when manually opening the throttle plate (TEST 1).
• Confirmed the TP sensor is receiving 5 Volts DC (TEST 2).
• Confirmed the TP sensor is receiving Ground (this test section).

CASE 2: The ultimeter DID NOT show 10 to 12 Volts. 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, you can conclude that one of two things are causing this lack of Ground:

• There's an open-circuit problem in the Ground wire between the TP sensor harness connector and the fuel injection computer's harness connector.
• The fuel injection computer has an internal problem (although this is extremely rare).

Although testing both of these conditions is beyond the scope of this tutorial, you have now eliminated the throttle position sensor (TPS) as the cause of the problem and/or the TP sensor diagnostic trouble code (DTC) illuminating the check engine light ( CEL).

More 2.8L Chevy S10 Pickup, GMC S15 Pickup, And GMC Sonoma Tutorials

You can find a complete list of tutorials for the 2.8L V6 Chevrolet S10 pickup, GMC S15 pickup, and GMC Sonoma in this index:

• GM 2.8L Index Of Articles.

Here's a sample of the articles, you'll find in the Index of Articles:

• How To Test The Fuel Pump (1988-1993 2.8L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
• How To Test Engine Compression (1988-1993 2.8L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
• How To Test The EGR Valve (1988-1993 2.8L Chevrolet S10 Pickup, GMC S15 Pickup, GMC Sonoma).
• How To Test The Starter Motor (1988-1993 2.8L V6 Chevrolet S10 Pickup, GMC S15 Pickup).