How To Test The TPS (1992-1997 3.9L V6 Dodge Ram Van)

To check if the throttle position sensor (TPS) is good or bad, on your 1992-1997 3.9L V6 Ram van, you just need a multimeter (no scan tool is needed).

With just three easy tests, that are explained step-by-step, you'll be able to quickly see if your TP sensor is OK or it's toast.

ES You can find this tutorial in Spanish here: Cómo Probar El Sensor De Posición Del Acelerador —Sensor TPS (1992-1997 3.9L V6 Dodge Ram Van) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 3.9L V6 Dodge Ram B150 Van: 1992, 1993.
• 3.9L V6 Dodge Ram B250 Van: 1992, 1993.
• 3.9L V6 Dodge Ram B1500 Van: 1994, 1995, 1996, 1997.
• 3.9L V6 Dodge Ram B2500 Van: 1994, 1995, 1996, 1997.

OTHER TPS SENSOR TESTS:

• How To Test The TPS (1989-1990 3.9L V6 Dodge Ram Van).
• How To Test The TPS (1991 3.9L V6 Dodge Ram Van).
• How To Test The TPS (1997-2003 3.9L V6 Dodge Ram Van).

Symptoms Of A Bad Throttle Position Sensor

You probably already know that the accelerator pedal is linked to the throttle plate with a cable.

In a nutshell, this is how it all works:

• When you step on the accelerator pedal, the throttle plate opens up, letting more air flow into the engine.
• When you take your foot off the pedal, the throttle plate automatically closes, which then reduces the amount of airflow entering the engine.

This increase or decrease in airflow, caused by the throttle plate angle, is tracked by the throttle position sensor and sent in real time to your Dodge Ram van's fuel injection computer.

If your TP sensor goes bad, you're going to notice your engine's performance dropping off a cliff. Let's look at some common symptoms you might see:

• OBD-I trouble codes: On the 1992-1995 vans, these codes will light up your check engine light (CEL):
  • Code 24: TPS Voltage Is Too Low.
  • Code 24: TPS Voltage Is Too High.
• OBD-II trouble codes: On the 1996-1997 vans, one of these codes will light up your check engine light (CEL):
  • P0121: TPS Voltage Does Not Agree With MAP.
  • P0122: TPS Voltage Is Too Low.
  • P0123: TPS Voltage Is Too High.
• Engine won't start: The engine refuses to start no matter how much you crank it.
• Hard Starting: You'll probably find yourself needing to crank the engine several times before it actually kicks in.
• Engine hesitation: You might experience a brief pause or stumble when you step on the gas and accelerate, usually happens when starting from a stop or while driving.
• Lack of power: You can feel a significant drop in power when you press the gas pedal.
• Poor gas mileage: The fuel injection system switches to 'limp-in' mode and reduces engine power (to protect your engine from further damage). This means it adds more fuel than usual, and as a result, your gas mileage takes a big hit.

Where To Buy The TPS And Save

The following links will help you to comparison shop for the TPS for your 3.9L V6 Dodge Ram van. I think they'll save you a few bucks:

If you're unsure if this TPS is compatible with your specific 3.9L V6 Dodge Ram van, no worries. Once you visit the site, they'll check and ensure it's the right one by asking for more details about your vehicle. If it doesn't fit, they'll help find the correct one.

TEST 1: Testing The TPS Voltage Signal

To wrap our heads around the test we're about to do, here's a simple breakdown of how the TPS works:

• Closed throttle: When the throttle plate is fully closed, the TPS outputs a low voltage of around 0.3 to 0.9 Volts DC.
• Throttle opening: As the throttle plate opens, the TPS gradually increases the voltage it generates.
• Wide Open Throttle (WOT): When you're at full throttle, the TPS usually produces around 4.5 Volts DC.
• Throttle closing: As the throttle plate closes, the voltage drops back down to its closed throttle value.

Basically, if your TPS isn't working correctly, you won't see its voltage output change as you open or close the throttle.

NOTE: You'll need a multimeter to be able to test the throttle position sensor. If you don't have one, this is the one I use and recommend: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (Amazon affiliate link).

IMPORTANT: The TP sensor has to stay connected to its 3-wire electrical connector to check its voltage signal output. To check the signal, you'll want to use a back probe on the connector or a wire-piercing probe on the signal wire. You can find an example of this tool and where to buy it here: Goupchn 4mm Banana to Banana Plug Test Leads Kit, 15PCS Five Colors (Amazon affiliate link).

Let's get'er done!

1. 1

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

2. 2

   Set your multimeter to Volts DC mode.

3. 3

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

4. 4

   Connect the red multimeter test lead to the orange with dark blue stripe (ORG/DK BLU) wire using an appropriate tool.
   
   The ORG/DK BLU wire should be the middle wire coming out of the TP sensor's 3-wire sensor.
   
   NOTE: Remember, the TP sensor needs to stay connected to its electrical connector.

5. 5

   You should now see a voltage reading between 0.3 and 0.9 Volts DC when the throttle plate is closed.
   
   If it's not reading that, don't worry! Move on to the next step.

6. 6

   Slowly open the throttle by hand from the engine compartment. Don't use the gas pedal.

7. 7

   As you open the throttle, the voltage reading should increase.

8. 8

   When the throttle plate is completely open, your multimeter should display a voltage reading between 3.5 and 4.5 Volts DC.

9. 9

   Now, slowly close the throttle plate.

10. 10

    The voltage reading should drop back down to what it was when the throttle was closed.

11. 11

    Tap the throttle position sensor with the handle of a screwdriver while opening and closing the throttle.
    
    If the TPS is working correctly, tapping it won't change its voltage output. But if the TPS is faulty, tapping it will cause the voltage signal to glitch out.

Let's figure out what's going on:

CASE 1: When you opened or closed the throttle plate, the TPS signal voltage changed accordingly. That's exactly what we need to see. This confirms your throttle position sensor is working correctly.

It also confirms that the TPS is getting both power and Ground from the fuel injection computer.

CASE 2: The TPS signal voltage stayed stuck at one value while you moved the throttle plate. Generally, this means the TPS is faulty.

To really make sure of this, we have to check that the TPS is getting power and Ground. Go to: TEST 2: Making Sure The TPS Is Receiving 5 Volts.

CASE 3: The multimeter showed no voltage during the test. It sounds like the TPS is bad.

Before you run out and replace it, double-check that it's getting power and Ground. Head over to: TEST 2: Making Sure The TPS Is Receiving 5 Volts.

TEST 2: Making Sure The TPS Is Receiving 5 Volts

There's a good chance the TP sensor's voltage signal is stuck (at that one value) because it's probably not getting power.

For our second test, we'll check that the violet with white stripe (VIO/WHT) wire is supplying a voltage between 4.5 and 5 Volts DC.

The VIO/WHT wire connects to the female terminal labeled with number 1 in the illustration above.

To make sure the VIO/WHT wire is actually delivering 5 Volts, we're going to test it with a multimeter.

Let's get right to it!

1. 1

   Disconnect the TP sensor from its connector.

2. 2

   Select the DC Volts mode on your multimeter.

3. 3

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

4. 4

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

5. 5

   Gently probe terminal 1 of the TP sensor's 3-wire connector with the red multimeter test lead.
   
   NOTE: Confirm that the VIO/WHT wire connects to terminal number 1.

6. 6

   You should see a reading of 4.5 to 5 Volts DC on your multimeter.

Let's look at your test results:

CASE 1: You're seeing 4.5 to 5 Volts. It means the TPS is getting power, which is exactly what we want to see.

For the final check, let's make sure the TPS is also receiving Ground. You can find the instructions here: TEST 3: Making Sure The TPS Is Receiving Ground.

CASE 1: You don't see 4.5 to 5 Volts. Without power, the TP sensor simply won't generate its variable voltage signal.

The most common causes of these missing 5 Volts are:

• An open-circuit problem in the wire between the TP sensor's 3-wire connector and the fuel injection computer's connector.
• An internal fault within the computer itself (although very rare).

Troubleshooting this problem isn't covered in this tutorial, but you now know that the TP sensor is OK. Your next step is to figure out what's stopping that voltage from reaching the sensor.

TEST 3: Making Sure The TPS Is Receiving Ground

So far, your previous two tests have found that:

• TEST 1: Opening or closing the throttle plate doesn't change the TPS voltage signal.
• TEST 2: Power's being delivered to the TP sensor.

Now, in this final test section, we're gonna confirm that the black with blue stripe (BLK/LT BLU) wire is supplying Ground to the TP sensor.

The terminal I've labeled with the number 3 in the illustration above, is the one that connects to the BLK/LT BLU wire.

We'll use a multimeter voltage test to make sure the BLK/LT BLU wire's delivering Ground.

IMPORTANT: Ground is provided to the sensor by the fuel injection computer. It's important that you don't directly connect this circuit to battery 12 Volts –or you're gonna fry the computer! The multimeter voltage test I'm suggesting is a safe and simple way to check for Ground in this circuit.

Here's how to check for Ground:

1. 1

   Disconnect the TP sensor from its connector.

2. 2

   Select the DC Volts mode on your multimeter.

3. 3

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

4. 4

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

5. 5

   Gently probe terminal 3 of the TP sensor's 3-wire connector with the black multimeter test lead.
   
   NOTE: Confirm that the BLK/LT BLU wire connects to terminal number 3.

6. 6

   You should see a reading of 10 to 12 Volts DC on your multimeter.

OK, let's find out what your test results mean:

CASE 1: Ground is present. This confirms the TP sensor is getting Ground.

Now, if you've confirmed the following conditions, your TPS needs is bad and needs replacement:

• The TP sensor isn't sending out a voltage signal that changes when you move the throttle plate (TEST 1).
• The TP sensor is receiving 4.5 to 5 Volts (TEST 2).
• You've confirmed it's getting Ground here.

CASE 2: Ground is not present. Double-check you're testing the right terminal.

If your multimeter still isn't showing 10 to 12 Volts, the throttle position sensor itself is fine. The problem causing the sensor to not generate it's variable voltage signal is it's the lack of Ground.

The most common causes of this missing Ground are:

• An open-circuit problem in the wire between the TP sensor's 3-wire connector and the fuel injection computer's connector.
• An internal fault within the computer itself (although very rare).

Troubleshooting this problem isn't covered in this tutorial, but you now know that the TP sensor is OK. Your next step is to figure out what's keeping Ground (from the computer) from reaching the sensor.

More 3.9L V6 Dodge Ram Van Tutorials

You can find a complete list of 3.9L V6 Dodge Ram van tutorials in this index:

• 3.9L V6 Dodge Ram Van Index Of Articles.

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

• How To Test The Engine Compression (1989-2003 3.9L V6 Dodge Ram Van).
• How To Test For A Blown Head Gasket (1989-2003 3.9L V6 Dodge Ram Van).
• How To Test The Fuel Pump (1992-2003 3.9L V6 Dodge Ram Van).
• How To Test The MAP Sensor (1992-1997 3.9L V6 Dodge Ram Van).