How To Test The Throttle Position Sensor (1992-1993 3.3L V6 Pontiac Grand Am)

TEST 2: Making Sure The TPS Is Receiving 5 Volts

If you've reached this point, then the result of TEST 1 indicated that the sensor's voltage signal is not increasing/decreasing as the throttle plate opens/closes.

There's a good chance that this is the result of the TPS not receiving power (5 Volts DC).

The wire that supplies these 5 Volts to the sensor is the gray (GRY) wire that connects to the terminal labeled with the letter A in the photo above.

We'll perform a simple multimeter voltage test to confirm the presence of these 5 Volts (with the key on but the engine off).

If the GRY wire is indeed supplying 5 Volts to the TPS, then our next step is to make sure that it's receiving Ground (TEST 3).

OK, let's get started:

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 (and using the appropriate tool), 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 interpret your test results:

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

Now that you have confirmed that your 3.3L Pontiac Grand Am's TPS is getting 5 Volts, the next step is to make sure it's getting Ground. Go to: TEST 3: Making Sure The TPS Is Getting Ground.

CASE 2: The GRY wire IS NOT feeding the TPS with 5 Volts. Without these 5 Volts the TPS, on your 3.3L Pontiac Grand Am, will not function.

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

TEST 3: Making Sure The TPS Is Getting Ground

Up to this point, you have confirmed:

• That the TPS signal voltage is not increasing/decreasing as you open/close the throttle plate (TEST 1).
• That the TPS is receiving 5 Volts DC (TEST 2).

Now we need to make sure that your 3.3L Pontiac Grand Am's TPS is receiving Ground.

The wire that supplies Ground to the sensor is the black (BLK) wire that connects to the terminal labeled with the letter C in the photo above.

Checking for the presence of Ground in the BLK wire is just a matter of doing a multimeter voltage test.

IMPORTANT: Be careful and don't short the Ground wire to battery power or you'll fry the fuel injection computer. The multimeter voltage test suggested below (for testing the Ground circuit) is a safe and accurate test.

This is what you'll need to do:

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 (and using the appropriate tool), gently probe the terminal labeled with the letter C.
   
   Terminal C 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 and it confirms that the TPS is getting Ground.

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.

More 3.3L Pontiac Grand Am Tutorials

You can find a complete list of 3.3L Pontiac Grand Am tutorials in this index:

• GM 3.3L Index Of Articles.

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

• How To Test Engine Compression Test (3.3L V6 Pontiac Grand Am).
• How To Test A Blown Head Gasket (3.3L V6 Pontiac Grand Am).
• How To Test The MAF Sensor (3.3L V6 Pontiac Grand Am).
• What Does A MAF Sensor Do? (3.3L V6 Pontiac Grand Am).