If you're trying to figure out whether the throttle position sensor (TPS) on your 1992–1997 V8 Ram van is working properly or not, I can tell you that all you need to do is perform 3 simple multimeter tests on it —no scan tool required.
In this tutorial, I've laid out my method of troubleshooting the TP sensor in a step-by-step format. With your test results, you'll be able to tell right away if your TPS is functioning correctly or if it's shot.
Contents of this tutorial:
- Symptoms Of A Bad Throttle Position Sensor.
- Throttle Position Sensor Operation Basics.
- Where To Buy The TPS And Save.
- TEST 1: Testing The TPS Voltage Signal.
- TEST 2: Making Sure The TPS Is Receiving 5 Volts.
- TEST 3: Making Sure The TPS Is Receiving Ground.
- More 5.2L, 5.9L V8 Dodge Ram Van Tutorials.
APPLIES TO: This tutorial applies to the following vehicles:
- 1992-1994:
- Dodge Ram B150 Van 5.2L V8: 1992, 1993, 1994.
- Dodge Ram B250 Van 5.2L V8: 1992, 1993, 1994.
- Dodge Ram B250 Van 5.9L V8: 1992, 1993, 1994.
- Dodge Ram B350 Van 5.9L V8: 1992, 1993, 1994.
- 1995-1997:
- Dodge Ram B1500 Van 5.2L V8: 1995, 1996, 1997.
- Dodge Ram B2500 Van 5.2L V8: 1995, 1996, 1997.
- Dodge Ram B3500 Van 5.2L V8: 1995, 1996, 1997.
- Dodge Ram B2500 Van 5.9L V8: 1995, 1996, 1997.
- Dodge Ram B3500 Van 5.9L V8: 1995, 1996, 1997.
Symptoms Of A Bad Throttle Position Sensor
Chances are, you already know that your accelerator pedal is connected to the throttle plate by a cable.
Here's a quick breakdown of how the system works:
- Pressing the accelerator pedal causes the throttle plate to open up, allowing more air to enter the engine.
- Releasing the pedal makes the throttle plate close, which limits the airflow going into the engine.
The throttle position sensor monitors this change in the throttle plate angle and sends that data directly to your Dodge Ram van's fuel injection computer in real time.
When the TPS fails, you'll likely notice a drastic change in how your van's engine performs. Here are some of the most common symptoms:
- OBD-I diagnostic codes: On 1992–1995 models, this code will trigger the check engine light (CEL):
- Code 24: TPS voltage Is Reading Too Low Or Too High.
- OBD-II diagnostic codes: On 1996–1997 models, you might see one of these codes causing the CEL to light up:
- P0121: TPS Voltage Doesn't Match What The MAP Sensor Is Seeing.
- P0122: TPS Voltage Is Lower Than It Should Be.
- P0123: TPS Voltage Is Higher Than Normal.
- Engine won't start: No matter how long you crank the engine, it doesn't start.
- Difficult starting: It may take several tries to get the engine to start.
- Hesitation on acceleration: You might feel the engine stumble or pause when you hit the gas, especially when pulling away from a stop or speeding up on the road.
- Reduced engine power: Stepping on the gas doesn't give you the response you expect —it feels sluggish or weak.
- Bad gas mileage: The computer switches to its 'limp-in' mode to prevent engine damage. This dumps more fuel than needed into the engine, killing your gas mileage.
Throttle Position Sensor Operation Basics
Before we dive into the actual test, let's quickly go over how the throttle position sensor (TPS) functions:
- Throttle fully closed: When the throttle plate is shut all the way (foot off the gas pedal), the TPS sends out a low voltage —typically between 0.3 and 0.9 Volts DC.
- Throttle begins to open: As you press the accelerator and the plate opens, the TPS voltage increases smoothly.
- Wide Open Throttle (WOT): At maximum throttle, the sensor should read close to 4.5 Volts DC.
- Throttle closing again: When the throttle plate returns to its closed position, the voltage drops back down to the original low reading.
In a nutshell, if the TPS is faulty, you won't see this voltage change as you move the throttle from closed to open and back.
Where To Buy The TPS And Save
The following links will help you to comparison shop for the TPS for your V8 Dodge Ram van. I think they'll save you a few bucks:
If you're unsure if this TPS is compatible with your specific V8 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 get started, we're gonna tap into the TPS signal wire —this is the middle wire on the sensor's 3-wire connector — using a multimeter set to Volts DC mode.
Next, we'll manually open and close the throttle plate from the engine compartment and watch the voltage reading. As the throttle opens, the TPS voltage should rise. As it closes, the voltage should drop back down to its starting value.
If the TPS is bad, the voltage reading will stay the same no matter how much you move the throttle plate —it won't respond to changes in angle.
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 with NCV Feature, Mastech MS8268 Upgraded, MS88 (at: amazon.com).
IMPORTANT: To properly measure the voltage signal from the TP sensor, it must remain plugged into its 3-wire electrical connector. To access the signal, you'll need to either back probe the connector or use a wire-piercing tool on the signal wire. You can see an example of that tool and where to buy one here: Wire Piercing Probe.
Alright, let's get to work!
- 1
Attach the black lead from your multimeter to the battery's negative (-) terminal.
- 2
Switch your multimeter to Volts DC mode.
- 3
Turn the key to the ON position —but don't start the engine.
- 4
Using a suitable tool, connect the red multimeter lead to the orange with dark blue stripe (ORG/DK BLU) wire of the connector.
The ORG/DK BLU wire should be the center wire in the TP sensor's 3-wire connector.
NOTE: Keep the TP sensor connected to its connector while doing this test. - 5
You should now get a voltage reading between 0.3 and 0.9 Volts DC when the throttle is fully closed.
If the reading doesn't fall within that range, don't stress —just continue to the next step. - 6
Manually open the throttle from the engine bay. Avoid using the gas pedal for this part.
- 7
The voltage should steadily rise as the throttle opens.
- 8
At wide open throttle (WOT), your multimeter should show a voltage between 3.5 and 4.5 Volts DC.
- 9
Slowly close the throttle plate again.
- 10
The voltage should return to its original low reading from when the throttle was closed.
- 11
Lightly tap the throttle position sensor using the handle of a screwdriver while moving the throttle open and closed.
If the sensor is in good shape, tapping it won't affect the voltage. But if it's failing, you might see sudden voltage spikes or drops when you tap it.
Let's break down what the results mean:
CASE 1: The TPS voltage changed as you opened and closed the throttle. That's a good sign —it means the TPS is functioning as it should.
It also confirms that the sensor is receiving both Ground and 5V power from the fuel injection system.
CASE 2: The TPS voltage stayed stuck at a constant value while you moved the throttle. This usually points to a faulty TPS.
To be sure, we need to confirm that the sensor is getting both power and Ground. Head over to: TEST 2: Making Sure The TPS Is Receiving 5 Volts.
CASE 3: You didn't see any voltage at all during the test. That's another sign the TPS may be bad.
But before you go replacing anything, make sure it's actually getting the voltage it needs. We'll check this next here: TEST 2: Making Sure The TPS Is Receiving 5 Volts.