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.
Contents of this tutorial at a glance:
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.
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 with NCV Feature, Mastech MS8268 Upgraded, MS88 (at: amazon.com).
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: Wire Piercing Probe.
Let's get'er done!
- 1
Connect the black multimeter test lead to the negative (-) battery terminal.
- 2
Set your multimeter to Volts DC mode.
- 3
Turn the key to the ON position, but don't start the engine.
- 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
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
Slowly open the throttle by hand from the engine compartment. Don't use the gas pedal.
- 7
As you open the throttle, the voltage reading should increase.
- 8
When the throttle plate is completely open, your multimeter should display a voltage reading between 3.5 and 4.5 Volts DC.
- 9
Now, slowly close the throttle plate.
- 10
The voltage reading should drop back down to what it was when the throttle was closed.
- 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.