How To Test The TPS (1990, 1991 5.2L V8 Dodge Dakota)

This tutorial will help you to test the throttle position sensor (TPS) on the 1990 and 1991 5.2L V8 Dodge Dakota.

The throttle position sensor can be tested with a multimeter. In this tutorial I'll show you how to test it with three simple tests.

With the results of your multimeter test, you'll be able to find out if the throttle position sensor is bad or not.

At the end of the tutorial I'm also going to show you where you can buy it and save a few bucks on its purchase.

You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (1990-1991 5.2L V8 Dodge Dakota) (at: autotecnico-online.com).

NOTE: This tutorial applies to the following vehicles since they use the exact same throttle position sensor: 1990, 1991 5.2L V8 Dodge Dakota.

Symptoms Of A Bad Throttle Position Sensor

As you're probably already aware, the TPS has the job of letting the fuel injection computer know how much the throttle plate opens and closes as you step on or step off the accelerator pedal.

With this information the computer can calculate how much fuel to inject into the engine.

Since the throttle position sensor is such a critical component of your Dodge Dakota's engine management system, when it fails, engine performance is going to suffer.

The most obvious symptom that you're going to see is the check engine light lit up by a throttle position sensor diagnostic trouble code.

  1. OBD I Code 24 TPS Voltage Too Low Or Too High.

You're also going to see one or more of the following symptoms:

  1. Won't pass the state mandated emissions test.
  2. Bad gas mileage.
  3. Lack of power, rough idle, or hesitation.
  4. Engine cranks a long time before starting.

Throttle Position Sensor (TPS) Circuit Descriptions

Throttle Position Sensor Pin Out. How To Test The TPS (1990, 1991 5.2L V8 Dodge Dakota)

The TPS is a 3 wire type sensor. This means that it has a power wire, a Ground wire and a signal wire. All three wires connect directly the fuel injection computer of your 5.2L V8 Dodge Dakota.

Since we're gonna' be testing all three wires, the table below has a brief description of each:

Terminal Wire Description
1 BLK/LT BLU Ground
2 ORG/LT BLU TPS Signal
3 VIO/WHT 5 Volts

The one thing that's going to help you to successfully diagnose the throttle position sensor and understand the three tests in this tutorial is knowing how the throttle position sensor works.

In a nutshell, the throttle position sensor creates a voltage signal that reacts to the throttle plate angle.

To be a bit more specific, when the throttle plate is closed, the throttle position sensor creates a voltage signal of about 0.5 to 0.9 Volts DC.

As the throttle plate opens (like when you step on the accelerator pedal), the TPS voltage signal starts to increase.

When the throttle plate opens to its maximum wide open position, the throttle position sensor produces a voltage of about 4.5 to 4.7 Volts DC.

When the throttle plate closes, the voltage signal decreases back to the original value. This process is repeated over and over as you step on or step off the accelerator pedal.

TEST 1: Testing The TPS Voltage Signal

Testing The TPS Voltage Signal. How To Test The TPS (1990, 1991 5.2L V8 Dodge Dakota)

All right, in this first test section we're gonna' test the throttle position sensor signal with a multimeter.

We're going to connect our multimeter to the orange with light blue stripe (ORG/LT BLU) wire of the TP sensor's 3 wire connector. This wire is identified with the number 2 in the photo above.

And as we open/close the throttle plate, we're going to see if the TPS voltage signal increases/decreases.

If the throttle position sensor is defective, you'll notice that the TPS voltage signal stays stuck in one number as you open and close the throttle plate

IMPORTANT: The throttle position sensor (TPS) must remain connected to its electrical connector for this test to function properly. To be able to access the voltage inside the signal wire, you'll need to use either a back probe or a wire piercing probe. You can see an example of this tool here: Wire Piercing Probe.

Let's get started:

  1. 1

    Place your multimeter in Volts DC mode.

  2. 2

    Connect the red test lead to the orange with light blue stripe (ORG/LT BLU) wire of the TP sensor harness connector.

  3. 3

    Ground the black multimeter test lead directly on the battery negative (-) post.

  4. 4

    Manually rotate the throttle.

    You'll get the best results by opening and closing the throttle directly on the throttle body instead of stepping on the accelerator pedal.

  5. 5

    The multimeter should show an increasing voltage as you (or your helper) open up the throttle.

    You'll get the best results by opening and closing the throttle directly on the throttle body instead of stepping on the accelerator pedal.

  6. 6

    The multimeter should show a decreasing voltage as you begin to close the throttle.

  7. 7

    Using a screwdriver's handle, gently tap the TP sensor as you open and close the throttle 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 decreased and increased as you opened and closed the throttle. This is the correct test result and lets you know that the TPS sensor is working correctly (not defective).

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. This test result usually indicates that the TPS sensor is defective.

To make sure the TPS sensor is truly defective we have to make sure that it's getting 5 Volts on the violet with white stripe (VIO/WHT) wire. For this test go to: TEST 2: Making Sure The TPS Has 5 Volts.

CASE 3: Multimeter DID NOT register any voltage. This test result usually indicates that the TPS sensor is defective.

To make sure the TPS sensor is truly defective we have to make sure that it's getting 5 Volts on the violet with white stripe (VIO/WHT) wire. For this test go to: TEST 2: Making Sure The TPS Has 5 Volts.

CASE 4: Tapping the TP sensor (with the screwdriver handle) caused gaps in the voltage reading. This test result tells you that the TPS sensor is defective.

Tapping the throttle position sensor with the screwdriver handle should not have any effect on the TPS voltage signal. Since it did, you can conclude that the TPS is defective.