How To Test The Throttle Position Sensor (1989-1993 3.3L V6 Buick, Oldsmobile)

This tutorial will help you to test the throttle position sensor (TPS) on 3.3L V6 equipped Buick and Oldsmobile vehicles.

Testing the TPS involves only 3 tests. All are explained in a step-by-step manner. You'll easily find out if TPS is bad or not.

This tutorial will also help you to diagnose the following OBD1 trouble codes: Code 21: Throttle Position Sensor Signal Voltage High. Code 22: Throttle Position Sensor Signal Voltage Low.

ES You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (1989-1993 3.3L V6 Buick, Oldsmobile) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 3.3L V6 Buick Century: 1989, 1990, 1991, 1992, 1993.
• 3.3L V6 Buick Skylark: 1989, 1990, 1991, 1992, 1993.
• 3.3L V6 Oldsmobile Achieva: 1992, 1993.
• 3.3L V6 Oldsmobile Calais: 1989, 1990, 1991.
• 3.3L V6 Oldsmobile Cutlass Ciera: 1989, 1990, 1991, 1992, 1993.

Symptoms Of A Bad Throttle Position Sensor

The throttle position sensor is a critical component of the engine management system. So when it fails, you'll definitely notice that something is wrong.

You're going to see one of the following OBD1 TPS diagnostic trouble codes lighting up the check engine light:

• 21: Throttle Position Sensor Signal Voltage High.
• 22: Throttle Position Sensor Signal Voltage Low.

You're also going to see one or more of the following symptoms:

• Engine hesitates when you step on the accelerator pedal.
• Lack of power when accelerating the vehicle.
• Bad gas mileage.
• Engine idle either too high or too low.
• Rough engine idle.
• The engine may start and immediately stall.
• The engine cranks but does not start.

You can find out more about the throttle position sensor here: What Does The Throttle Position Sensor Do? (3.3L V6 Buick, Oldsmobile).

Throttle Position Sensor (TPS) Circuit Descriptions

As you're probably already aware, there are 3 wires sticking out of the throttle position sensor's connector.

To successfully test the throttle position sensor, we need to know what each one of them does.

The following is a brief description of what each wire does:

Terminal	Wire	Description
A	Grey (GRY)	5 Volts
B	Blue (BLU)	TPS Signal
C	Black (BLK)	Ground

Where To Buy The TPS And Save

The following links will help you to comparison shop for the throttle position sensor (of known professional automotive brands- NO knockoffs) for your 3.3L V6 Buick (Oldsmobile).

1989-1992 Adjustable TPS:

1993 Non-Adjustable TPS:

NOTE: The 1989-1992 3.3L V6 vehicles use an adjustable TPS. The 1993 3.3L V6 vehicles use a non-adjustable TPS.

TEST 1: Testing The TPS Voltage Signal

The very first thing that we'll do, to start our TPS diagnostic, is to check the signal output of the sensor.

If all is OK with the TPS, you should see the TPS voltage signal increase as you open the throttle plate and it should decrease as you close the throttle plate.

For this test, we're going to connect the multimeter to the blue (BLU) wire of the sensor's 3-wire connector.

IMPORTANT: The throttle position sensor must remain connected to its connector to be able to access the signal inside the wire. You'll need to use either a wire piercing probe or a back probe. You can check out what this tool looks like (this is the one I use), and where to buy it, here: Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link).

Let's get started:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Connect the red multimeter test lead to the blue (BLU) wire of the TP sensor harness connector.
   
   The BLU wire connects to the terminal identified with the letter B in the photo above.
   
   NOTE: The TPS must remain connected to its connector to test the TPS voltage signal.

3. 3

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

4. 4

   Turn the key on but don't crank or start the engine.

5. 5

   Manually rotate the throttle plate.
   
   You'll get the best results by opening and closing the throttle plate directly on the throttle body instead of stepping on the accelerator pedal.

6. 6

   The multimeter should show an increasing voltage as you (or your helper) open up the throttle plate.

7. 7

   The multimeter should show a decreasing voltage as you begin to close the throttle plate.

8. 8

   Using a screwdriver's handle, gently tap the TP sensor as you open and close the throttle plate and observe the multimeter.
   
   The purpose (of tapping the TP sensor with the screwdriver's handle) is to see if the TP sensor shows gaps in the voltage signal. Why? Because a good TP sensor will show a continuous increasing or decreasing voltage signal even while getting tapped by the screw-driver's handle.

Let's analyze your test results:

CASE 1: The TPS voltage signal increased/decreased as you opened/closed the throttle plate. This is the correct test result and it indicates that the throttle position sensor is good.

With this test result you can also conclude that the TPS sensor is getting both power (5 Volts) and Ground from the fuel injection computer.

CASE 2: The TPS voltage signal DID NOT increase/decrease as you opened and closed the throttle plate. This test result usually indicates that the TPS sensor is defective.

To make sure the TPS sensor is bad the next step is to check that the GRY wire is feeding the TPS with 5 Volts. For this test go to: TEST 2: Making Sure The TPS Is Receiving 5 Volts.

CASE 3: The multimeter DID NOT register any voltage. This test result usually indicates that the TPS sensor is defective.

To make sure the TPS sensor is bad the next step is to check that the GRY wire is feeding the TPS with 5 Volts. For this test go to: TEST 2: Making Sure The TPS Is Receiving 5 Volts.

TEST 2: Making Sure The TPS Is Receiving 5 Volts

If in TEST 1, the throttle position sensor's signal did not increase/decrease, then there's a good chance that it might not be receiving power (5 Volts).

So in this test section, we're going to check that the wire labeled with the letter A is providing 5 Volts DC to the sensor.

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

If the wire is supplying 5 Volts DC to the TPS, then the next step is to make sure that the sensor is receiving 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 (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 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 3.3L 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 3.3L 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

So far your test results 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).

In this last test section, we're going to make sure that the TPS is receiving Ground.

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

We'll do a simple multimeter voltage test to check for the presence of Ground in the black (BLK) wire.

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 (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.

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 V6 Buick, Oldsmobile Tutorials

You can find a complete list of 3.3L V6 Buick (Oldsmobile) 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 Buick, Oldsmobile).
• How To Test A Blown Head Gasket (3.3L V6 Buick, Oldsmobile).
• How To Test The MAF Sensor (3.3L V6 Buick, Oldsmobile).
• What Does A MAF Sensor Do? (3.3L V6 Buick, Oldsmobile).