TEST 2: Making Sure The TPS Is Receiving 5 Volts
The throttle position sensor gets 5 Volts DC from the fuel injection computer.
These 5 Volts are fed to the sensor via the gray (GRY) wire of the TPS 3-wire connector.
The GRY wire connects to the terminal labeled with the letter A in the photo above.
In this section, we'll verify that the GRY wire provides 5 Volts by doing a multimeter voltage test (on terminal A).
These are the test steps:
- 1
Place your multimeter in Volts DC mode.
- 2
Disconnect the TPS from its electrical connector.
- 3
Turn the key the ON position but don't start the engine.
- 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
Connect the black multimeter test lead to the negative (-) battery terminal.
- 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 the 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 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 That The TPS Is Receiving Ground
The tests you've performed up to this point have confirmed the following:
- The TPS does not produce a voltage signal that increases or decreases as the throttle is opened and closed (TEST 1).
- The gray wire supplies 5 Volts to the sensor (TEST 2).
The last test we have to do is to verify that the TPS is receiving Ground, which is provided by the fuel injection computer.
The black (BLK) wire of the TPS 3-wire connector is the wire that delivers this Ground to the TPS.
The BLK wire connects to the female terminal labeled with the letter B in the photo above.
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
Place your multimeter in Volts DC mode.
- 2
Disconnect the TPS from its electrical connector.
- 3
Turn the key the ON position but don't start the engine.
- 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
Connect the red multimeter test lead to the positive (+) battery terminal.
- 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 bad and needs replacement 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.
An open-circuit problem in the BLK wire (between the throttle position sensor's connector and the fuel injection computer's connector) is usually the cause of this missing Ground.
More 3.1L Chevrolet And Pontiac Diagnostic Tutorials
You can find a complete list of 3.1L Chevrolet and Pontiac diagnostic tutorials in this index:
Here's a small sample of the tutorials you'll find in the index:
- How To Test The Fuel Pump (1990-1994 3.1L V6 Chevrolet And Pontiac Vehicles).
- How To Test The Alternator (1990-1994 3.1L V6 Chevrolet And Pontiac Vehicles).
- How To Test The Engine Compression (3.1L V6 Chevrolet And Pontiac Vehicles).
- How To Test The Starter Motor (1990-1994 3.1L V6 Chevrolet And Pontiac Vehicles).
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