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

TEST 2: Making Sure The TPS Is Getting 5 Volts

So far, your tests show that:

• The TPS voltage signal isn't changing when you open or close the throttle plate.

Now we're gonna check if the throttle position sensor (TPS) is actually getting power.

That power comes as 5 Volts DC, and it's sent by the fuel injection computer through the violet (VIO) or violet with white stripe (VIO/WHT) wire of the TPS connector.

Once we see it's getting the 5 Volts it needs, we'll move on to make sure it's also got a solid Ground in TEST 3.

NOTE: If you're probing the front of the TPS harness connector to test for voltage, be super careful not to damage the female terminal inside.

This is what you need to do:

1. 1

   Set your multimeter to Volts DC mode.

2. 2

   Unplug the TPS from its connector.

3. 3

   Connect the black test lead to the battery's negative (-) terminal.

4. 4

   Turn the key to ON, but don't crank nor start the engine.

5. 5

   Use the red test lead to gently probe terminal number 1 of the sensor's 3-wire connector.
   
   NOTE: Make sure this terminal corresponds to the VIO or VIO/WHT wire of the connector.

6. 6

   You should see 4.5 to 5 Volts DC on the multimeter.

Here's what the results mean:

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

Next, check if the BLK/LT BLU wire is sending Ground to the TPS. For that, head to: TEST 3: Making Sure The TPS Is Getting Ground.

CASE 2: No 4.5 to 5 Volts present. If the sensor's not getting 5 Volts, it won't send a signal.

Although it's beyond the scope of this tutorial to troubleshoot these missing 5 Volts, you're next step is to find out and restore them to the circuit.

The most likely reason for this missing voltage is a break 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:

• The TPS isn't sending a voltage signal that goes up or down on the ORG/DK BLU wire when the throttle opens or closes (TEST 1).
• The VIO or VIO/WHT wire on the TPS connector is supplying 5 Volts of power (TEST 2).

This last test checks if the black with light blue stripe (BLK/LT BLU) wire is giving the TPS Ground.

NOTE: Don't short this wire to the battery! Doing that can fry your Dodge Ram pickup's fuel injection computer.

Here's how to run the test:

1. 1

   Switch your multimeter to Volts DC mode.

2. 2

   Unplug the TPS from its connector.

3. 3

   Connect the red test lead to the battery's positive (+) terminal.

4. 4

   Turn the key to the ON position, but don't start the engine.

5. 5

   Use the black test lead to gently probe terminal number 3.
   
   NOTE: Make sure this terminal corresponds to the BLK/LT BLU wire of the connector.

6. 6

   If there's Ground in the wire, your multimeter should show 10 to 12 Volts DC.

Let's break down what your results mean:

CASE 1: You've got Ground in the BLK/LT BLU wire. That's the result you want.

If you've confirmed all three of these:

1. The TPS isn't putting out a changing signal when the throttle moves (TEST 1).
2. The TPS is getting power (TEST 2).
3. The BLK/LT BLU wire is supplying Ground (this test).

Then it's safe to say the TPS is bad and needs replacing.

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

CASE 2: No Ground in the BLK/LT BLU wire. Without it, the TPS won't be able to send a signal at all.

Although it's beyond the scope of this tutorial to troubleshoot this missing Ground, you're next step is to find out and restore it to the circuit.

The most likely reason for this missing Ground is a break in the wire between the TPS 3-wire connector and the fuel injection computer connector.

More 3.9L V6 Dodge Ram Pickup Tutorials

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

• 3.9L V6 Dodge Ram Pickup Index Of Articles.

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

• How To Test The Engine Compression (1989-2001 3.9L V6 Dodge Ram Pickup).
• How To Test The Fuel Pump (1992-2001 3.9L V6 Dodge Ram Pickup).
• How To Test The TPS (1992-1996 3.9L V6 Dodge Ram Pickup).
• How To Test The MAP Sensor (1992-1996 3.9L V6 Dodge Ram Pickup).