In this tutorial, I'm gonna' explain how to test the throttle position sensor (TPS) on the 2000, 2001, 2002, and 2003 3.9L V6 Dodge Dakota with a multimeter.
You'll be able to find out if the throttle position sensor is bad or not. You'll also be able to diagnose trouble codes: P0122 and P0123.
Contents of this tutorial at a glance:
You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (2000-2003 3.9L V6 Dodge Dakota) (at: autotecnico-online.com).
NOTE: This tutorial applies to the following vehicles since they use the exact same throttle position sensor: 2000, 2001, 2002, 2003 3.9L V6 Dodge Dakota.
Symptoms Of A Bad Throttle Position Sensor
The throttle position sensor is a critical component of the engine management system of your 2000-2003 3.9L V6 Dodge Dakota. It's job is to monitor and report the throttle plate angle to your Dodge Dakota's fuel injection computer (as you step on or step off the accelerator pedal).
So when it fails, your Dodge Dakota's 3.9L V6 engine is going to resent it. You're going to see one of the following TPS diagnostic trouble codes lighting up the check engine light:
- P0122 TPS Voltage Too Low (1996 3.9L Dodge Dakota).
- P0123 TPS Voltage Too High (1996 3.9L Dodge Dakota).
You're also going to see one or more of the following symptoms:
- Won't pass the state mandated emissions test.
- Bad gas mileage.
- Lack of power, rough idle, or hesitation.
- Engine cranks a long time before starting.
Throttle Position Sensor (TPS) Circuit Descriptions
To test the TPS we need to know what each of the 3 wires (coming out of its connector) does. The following table has a brief description of each:
| Terminal | Wire | Description |
|---|---|---|
| 1 | BLK/LT BLU | Ground |
| 2 | ORG/LT BLU | TPS Signal |
| 3 | ORG | 5 Volts |
In a nutshell, the throttle position sensor's signal voltage increases as the throttle plate opens. When the throttle plate is in its closed position, it'll produce a voltage signal of about 0.4 to 0.9 Volts DC.
When the throttle plate reaches its maximum wide open position, the TPS produces a voltage signal of about 4.5 Volts DC.
The cool thing is that we can test the TPS signal with a multimeter and that's how I'll show you how to do it in this tutorial.
Where To Buy The TPS And Save
The 2000-2003 3.9L V6 Dodge Dakota's TPS is not an expensive engine management component. The following links will help you to comparison shop and hopefully save you a few bucks on its purchase:
NOTE: The above throttle position sensor (TPS) fits the following vehicles: 2000, 2001, 2002, 2003 3.9L V6 Dodge Dakota.
TEST 1: Testing The TPS Voltage Signal
The wire that carries the TPS signal to your Dodge Dakota's fuel injection computer is the orange with light blue stripe (ORG/LT BLU) wire of its 3-wire connector.
This wire is labeled with the number 2 in the photo above and this is the wire that we're gonna' tap into to check the TPS voltage signal.
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.
These are the test steps:
- 1
Place your multimeter in Volts DC mode.
- 2
Connect the red test lead to the orange with light blue stripe (ORG/LT BLU) wire of the TP sensor harness connector.
- 3
Ground the black multimeter test lead directly on the battery negative (-) post.
- 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
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
The multimeter should show a decreasing voltage as you begin to close the throttle.
- 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.
This test result lets you know that the TPS sensor is working correctly (not defective) and that it's 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 these tests go to: TEST 2: Making Sure The TPS Has 5 Volts.
CASE 3: The 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 these tests go to: TEST 2: Making Sure The TPS Has 5 Volts.
