In this tutorial, I'm gonna' explain how to test the throttle position sensor (TPS) on the 1992-1996 3.9L V6 Dodge Dakota.
With your test results you'll be able to conclude that the throttle position sensor (TPS) is bad or not.
You'll also be able to diagnose the following TPS diagnostic trouble codes: OBD I code 26 (1992-1995 3.9L Dodge Dakota) and OBD II codes P0122 and P0123.
Contents of this tutorial at a glance:
You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (1992-1996 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: 1992, 1993, 1994, 1995, 1996 3.9L V6 Dodge Dakota.
WIRING DIAGRAM: You can find the fuel injection system wiring diagram here: Engine Management Sensor Circuit Diagram (1994-1995 3.9L V6 Dodge Dakota).
Symptoms Of A Bad Throttle Position Sensor
As you're problably aware, the throttle position sensor on your 3.9L Dodge Dakota is tasked with measuring the angle of the throttle plate in the throttle body.
The angle of the throttle plate changes as you step on or step off the accelerator pedal. As you step on the accelerator pedal, the throttle plate opens.
As you step off the accelerator pedal, the throttle plate closes. These changes are then measured and reported to the fuel injection computer by the throttle position sensor (TPS).
Since the throttle position sensor (TPS) is such an important component of the fuel injection system of your 1992-1996 3.9L Dodge Dakota, when it fails you're gonna' definitely feel the engine resent it.
You're going to see the following TPS diagnostic trouble code lighting up the check engine light:
- OBD I Code 24 TPS Voltage Too Low Or Too High (1992-1995 3.9L Dodge Dakota).
- OBD II Code P0122 TPS Voltage Too Low (1996 3.9L Dodge Dakota).
- OBD II Code 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
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 3.9L 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 |
Where To Buy The TPS And Save
The 1992-1996 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: 1992, 1993, 1994, 1995, 1996 3.9L V6 Dodge Dakota.
TEST 1: Testing The TPS Voltage Signal
In a throttle position sensor that's working correctly, the TPS signal will increase as the throttle plate opens till the throttle plate reaches its maximum wide open position.
As the throttle plate starts to close, the TPS voltage signal will start to decrease till the throttle plate reaches its closed throttle position.
At the closed throttle position, you'll normally see a TPS voltage signal of about 0.4 to 0.9 Volts DC. As mentioned before, this voltage signal will increase as the throttle plate opens.
At the wide open throttle position, you'll see about 4.5 to 4.7 Volts DC.
For our first test, we're gonna' check the TPS signal and make sure that it's increasing as we open the throttle plate and decreases as we 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
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 increased/decreased as you opened/closed the throttle plate. 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 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.
