How To Test The TPS (1989-1990 5.2L, 5.9L V8 Dodge Ram Van)

TEST 2: Making Sure The TPS Is Getting 5 Volts

Your results from TEST 1 show the following:

• The TPS voltage stays locked at one value as the throttle plate is moved to the wide open position.

Now, we'll verify whether the TP sensor is getting power through the violet (VIO) or violet with white stripe (VIO/WHT) wire of the TPS's 3-wire connector.

Once we confirm that the sensor is receiving the required 5-volt supply, we'll move on to TEST 3 to check the Ground connection.

NOTE: Be very careful when probing the front of the connector terminals —it's easy to damage them if you push the probe too hard into the terminal.

Here's how to run this power supply test:

1. 1

   Switch your multimeter to the DC Volts setting.

2. 2

   Unplug the TPS from its 3-wire connector.

3. 3

   Place the black multimeter lead on the battery's negative (-) terminal.

4. 4

   Turn the ignition key to ON. Do not crank or start the engine.

5. 5

   Carefully probe terminal 1 of the connector using the red multimeter lead.
   
   Remember, you're checking the 3-wire connector that plugs into the sensor —not the terminals on the sensor itself.
   
   NOTE: Be sure the terminal you're testing connects to the VIO or VIO/WHT wire.

6. 6

   You should get a reading between 4.5 and 5 Volts DC.

Let's break down what your test results tell you:

CASE 1: Voltage reading is between 4.5 and 5 Volts. That's exactly what we want to see.

The next step is to confirm that the BLK/LT BLU wire is delivering a solid Ground connection to the sensor. Go to: TEST 3: Making Sure The TPS Is Getting Ground.

CASE 2: No voltage detected. If you're not seeing 4.5 to 5 Volts, the TPS won't be able to send out a signal.

Diagnosing why power is missing goes beyond this guide, but your next move is to trace the cause and restore the 5-volt reference to the circuit.

The most frequent cause of missing voltage is an open-circuit (usually a break in the wire) between the TPS connector and the fuel injection computer (ECU) connector.

TEST 3: Making Sure The TPS Is Getting Ground

Your TPS testing so far has confirmed the following:

• TEST 1: The TPS signal voltage remains unchanged when the throttle plate is opened or closed.
• TEST 2: The sensor is receiving its 5V power supply from the fuel injection computer.

Now it's time for the final check —we'll test whether the black with light blue stripe (BLK/LT BLU) wire is providing a Ground connection.

CAUTION: Never apply 12 Volts directly to this wire —doing so can seriously damage your Dodge Ram van's fuel injection computer.

Here's how to perform this test safely:

1. 1

   Set your multimeter to measure DC voltage.

2. 2

   Disconnect the TPS from the 3-wire connector.

3. 3

   Attach the red multimeter lead to the battery's positive (+) terminal.

4. 4

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

5. 5

   Use the black multimeter lead to carefully probe terminal 3 of the TPS connector.
   
   NOTE: Make sure this terminal corresponds to the BLK/LT BLU wire in the connector.

6. 6

   You should see a voltage reading between 10 and 12 Volts DC.

Now let's go over what your results mean:

CASE 1: The BLK/LT BLU wire is providing a proper Ground. That's the result we want.

If the following are true:

1. The TPS isn't generating a variable signal as the throttle moves (TEST 1).
2. The sensor is getting power (TEST 2).
3. And the Ground wire is confirmed working (this test).

Then it's safe to say the TPS has failed and needs to be replaced.

If you're looking to save some money, take a look at my suggestions here: Where To Buy The TPS And Save.

CASE 2: No Ground detected from the BLK/LT BLU wire. Without a solid Ground, the TPS can't send out a signal.

Diagnosing the missing Ground goes beyond the scope of this tutorial, but your next step is to trace the issue and repair the Ground connection.

The most frequent culprit for this kind of problem is an open or broken circuit between the TPS connector and the fuel injection computer.

More 5.2L, 5.9L V8 Dodge Ram Van Tutorials

I've written quite a few 5.2L/5.9L V8 Dodge Ram van 'how to test' tutorials. You can find them in this index:

• 5.2L, 5.9L V8 Dodge Ram Van Index Of Articles.