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.
Contents of this tutorial at a glance:
- Symptoms Of A Bad Throttle Position Sensor.
- Throttle Position Sensor (TPS) Circuit Descriptions.
- Where To Buy The TPS And Save.
- TEST 1: Testing The TPS Voltage Signal.
- TEST 2: Making Sure The TPS Is Receiving 5 Volts.
- TEST 3: Making Sure That The TPS Is Receiving Ground.
- More 3.3L V6 Buick, Oldsmobile Tutorials.
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, and where to buy it, here: Wire Piercing Probe.
Let's get started:
- 1
Place your multimeter in Volts DC mode.
- 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
Connect the black multimeter test lead directly on the battery negative (-) post.
- 4
Turn the key on but don't crank or start the engine.
- 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
The multimeter should show an increasing voltage as you (or your helper) open up the throttle plate.
- 7
The multimeter should show a decreasing voltage as you begin to close the throttle plate.
- 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.
