How To Test The TPS (1989-1990 3.9L V6 Dodge Ram Van)

TEST 2: Making Sure The TPS Is Getting 5 Volts

Your TEST 1 result indicates:

• The TPS voltage signal remains stuck in one value when you open the throttle plate to its wide open position.

We're now going to check that the throttle position sensor (TPS) receiving power from the violet (VIO) or violet with white stripe (VIO/WHT) wire of the TPS 3-wire connector.

Once we confirm that the TPS is receiving the required 5 Volts, we'll proceed to TEST 3 and check that it's also getting Ground.

NOTE: When testing the front of the terminals (of the TPS 3-wire connector), exercise extreme caution to avoid damaging them.

This is what you need to do:

1. 1

   Set your multimeter to its Volt DC setting.

2. 2

   Disconnect the TPS from its 3-wire connector.

3. 3

   Attach the black test probe to the battery's negative (-) terminal.

4. 4

   Turn on the ignition switch, but don't crank or start the engine.

5. 5

   Gently probe terminal number 1 with the red multimeter test lead.
   
   Remember, you're testing the terminal of the sensor's 3-wire connector.
   
   NOTE: Make sure this terminal corresponds to the VIO or VIO/WHT wire of the 3-wire TPS connector.

6. 6

   You should see approximately 4.5 to 5 Volts DC.

Let's take a look at what your test results mean:

CASE 1: 4.5 to 5 Volts are present. That's the result we're looking for.

Next stop is to make sure the BLK/LT BLU wire is providing Ground to the TPS. Proceed to: TEST 3: Making Sure The TPS Is Getting Ground.

CASE 2: The specified voltage IS NOT present. If the sensor is not receiving 4.5 to 5 Volts, it won't generate a TPS signal.

Troubleshooting these missing 5 Volts falls outside of this tutorial's scope, but your next step would be to investigate why they're missing and restore it to the circuit.

The most common cause of this missing voltage issue is an open-circuit problem in the wire between the TPS 3-wire connector and the fuel injection computer connector.

TEST 3: Making Sure The TPS Is Getting Ground

Your TPS tests have now confirmed the following:

• TEST 1: The TPS signal voltage is stuck as you open/close the throttle plate.
• TEST 2: The TP sensor is getting power from the fuel injection computer.

For our final test, we'll see if the black with light blue stripe (BLK/LT BLU) wire is delivering Ground.

CAUTION: Do not short this wire to the battery 12 Volts, as doing so will damage your Dodge Ram van's fuel injection computer.

Let's begin:

1. 1

   Set your multimeter to the Volts DC mode.

2. 2

   Disconnect the TPS from its 3-wire connector.

3. 3

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

4. 4

   Turn the ignition switch to the ON position, but don't crank or start the engine.

5. 5

   With the black multimeter test lead, carefully probe terminal number 3 of the 3-wire connector.
   
   NOTE: Verify that this terminal corresponds to the BLK/LT BLU wire of the 3-wire connector.

6. 6

   Your multimeter should display a voltage reading between 10 and 12 Volts DC.

Let's break down your results:

CASE 1: The BLK/LT BLU wire is supplying Ground. That's the outcome you're looking for.

If you have confirmed:

1. The TPS isn't sending out a variable voltage signal when the throttle moves (TEST 1).
2. The TPS is receiving power (TEST 2).
3. The BLK/LT BLU wire is providing Ground (this test).

If all three conditions are met, it's safe to conclude that the TPS is fried and requires replacement.

If you're looking to save some bucks, check out my recommendations: Where To Buy The TPS And Save.

CASE 2: The BLK/LT BLU wire is not delivering Ground. Without Ground, the TPS is won't generate and TP signal.

Troubleshooting this missing Ground falls outside of this tutorial's scope, but your next step would be to investigate why it's missing and restore it to the circuit.

The most common cause of this missing Ground is an open-circuit problem in the wire between the TPS 3-wire connector and the fuel injection computer connector.

More 3.9L V6 Dodge Ram Van Tutorials

I've written quite a few 3.9L V6 Dodge Ram van 'how to test' tutorials. You can find them in this index:

• 3.9L V6 Dodge Ram Van Index Of Articles.

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

• How To Test The Engine Compression (1989-2003 3.9L V6 Dodge Ram Van).
• How To Test For A Blown Head Gasket (1989-2003 3.9L V6 Dodge Ram Van).
• How To Test The Fuel Pump (1989-1991 3.9L V6 Dodge Ram Van).
• How To Test The TPS (1997-2003 3.9L V6 Dodge Ram Van).