How To Test The TPS (1989-1993 3.1L V6 Buick Regal, Oldsmobile Cutlass Supreme)

TEST 2: Making Sure The TPS Is Receiving 5 Volts

Like every other electrical component on your vehicle, the throttle position sensor requires power and Ground to function.

In this section, we'll verify that the TPS is receiving 5 Volts DC from the fuel injection computer.

The wire that supplies that 5 Volts (from the computer to the TPS) is the wire labeled with the letter A in the photo above.

The wire that connects to the terminal labeled with the letter A is the TPS connector's grey (GRY) wire.

If the wire supplies 5 Volts DC to the TPS, the next step is ensuring that the sensor receives Ground (TEST 3).

Let's get testing:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Disconnect the TPS from its electrical connector.

3. 3

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

4. 4

   With the red multimeter test lead, gently probe the female terminal labeled with the letter A.
   
   Terminal A connects to the GRY wire of the connector.

5. 5

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

6. 6

   Your multimeter should read 4.5 to 5 Volts DC.

Let's analyze your test results:

CASE 1: The GRY wire is feeding the TPS with 5 Volts. This is the correct test result.

Now that you have confirmed that your 3.1L V6 Buick (Oldsmobile)'s TPS is getting 5 Volts, the next step is to make sure it's getting Ground. Go to: TEST 3: Making Sure That The TPS Is Receiving Ground.

CASE 2: The GRY wire IS NOT feeding the TPS with 5 Volts. Without these 5 Volts the TPS, on your 3.1L V6 Buick (Oldsmobile), will not function.

These missing 5 Volts are usually the result of an open-circuit problem in the GRY wire between the TPS sensor's connector and the fuel injection computer's connector.

TEST 3: Making Sure That The TPS Is Receiving Ground

Up to this point, your TPS diagnostic tests have confirmed the following:

• The TPS voltage signal does not increase/decrease when you open/close the throttle plate (TEST 1).
• The TPS is receiving 5 Volts from the fuel injection computer (TEST 2).

For our final test, let's check that the black (BLK) wire that connects to the terminal labeled with the letter B supplies Ground to the throttle position sensor.

IMPORTANT: Be careful not to short the Ground wire to battery power, or you will fry the fuel injection computer. The multimeter voltage test suggested below (to test the Ground circuit) is a safe and accurate test.

These are the test steps:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Disconnect the TPS from its electrical connector.

3. 3

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

4. 4

   With the black multimeter test lead, gently probe the terminal labeled with the letter B.
   
   Terminal B connects to the BLK wire of the connector.

5. 5

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

6. 6

   Your multimeter should read 10 to 12 Volts DC.

Let's analyze your test results:

CASE 1: The BLK wire is feeding Ground to the TPS. This is the correct test result.

You can correctly conclude that the TPS is defective if you have:

• Confirmed that the TPS voltage signal does not increase/decrease as you opened/closed the throttle plate (TEST 1).
• Confirmed that the TPS is getting 5 Volts (TEST 2).
• Confirmed, in this test section, that the TPS is getting Ground.

CASE 2: The BLK wire IS NOT feeding Ground to the TPS. Without Ground the TPS will not function.

This missing Ground is usually caused by an open-circuit problem in the BLK wire between the throttle position sensor's connector and the fuel injection computer's connector.