If you're dealing with a throttle response issue or the check engine light is showing TPS-related codes like P0121, P0122, or P0123, you're in the right place.
In this step-by-step tutorial, I'll show you exactly how to test the throttle position sensor (TPS) on your 2002–2007 4.7L V8 Dodge Ram pickup using just a basic multimeter.
You'll learn how to check for a proper TPS signal, 5 Volt reference, and Ground —the three key things the TPS needs to work correctly.
Let's get started and find out if that TPS sensor really is the problem or if the issue lies somewhere else in the circuit.
Contents of this tutorial:
APPLIES TO: This tutorial applies to the following vehicles:
- 4.7L V8 Dodge Ram 1500 Pickup: 2002, 2003, 2004, 2005, 2006, 2007.
TPS TROUBLE CODES EXPLAINED:
- P0121 TPS Code Explained (2002-2007 4.7L V8 Dodge Ram Pickup).
- P0122 TPS Code Explained (2002-2007 4.7L V8 Dodge Ram Pickup).
- P0123 TPS Code Explained (2002-2007 4.7L V8 Dodge Ram Pickup).
TPS WIRING DIAGRAMS:
- Sensor Power And Ground Circuit Wiring Diagram (2002 4.7L V8 Dodge Ram Pickup).
- Sensor Power And Ground Circuit Wiring Diagram (2003 4.7L V8 Dodge Ram Pickup).
- Sensor Power And Ground Circuit Wiring Diagram (2004-2005 4.7L V8 Dodge Ram Pickup).
- Sensor Power And Ground Circuit Wiring Diagram (2006-2007 4.7L V8 Dodge Ram Pickup).
Symptoms Of A Bad TPS Sensor
A bad throttle position sensor (TPS) on your 2002–2007 4.7L V8 Dodge Ram pickup can cause all sorts of driveability issues. The most common symptoms include:
- Engine idle issues: Unstable or rough idle.
- Hesitation: Engine hesitation or stumbling during acceleration.
- Erratic idle speed: Sudden surging or bucking while cruising.
- Shifting issues: Transmission shifting problems, especially hard or delayed shifts.
- Bad gas mileage: Poor fuel economy and lack of power.
When the TPS sensor starts to fail, the PCM (Powertrain Control Module) may store one or more TPS-related trouble codes. You'll see one of the following:
- P0121: TPS Voltage Not Plausible.
- P0122: TPS Voltage Low.
- P0123: TPS Voltage High.
If you're seeing any of these codes or experiencing the symptoms above, then testing the TPS sensor is the logical next step —and that's exactly what I'll walk you through in this tutorial.
NOTE: I've written in-depth tutorials for each of these codes —P0121, P0122, and P0123— to help you understand exactly what they mean and how to troubleshoot them.
- P0121 TPS Code Explained (2002-2007 4.7L V8 Dodge Ram Pickup).
- P0122 TPS Code Explained (2002-2007 4.7L V8 Dodge Ram Pickup).
- P0123 TPS Code Explained (2002-2007 4.7L V8 Dodge Ram Pickup).
Where To Buy The TPS And Save
If you've confirmed the TPS is bad and you're ready to replace it, here are two trusted options I recommend. These links point to name-brand parts that fit the 2002–2007 4.7L V8 Dodge Ram pickup —parts I’d use myself. Buying through these links helps support the site and keeps the tutorials coming, at no extra cost to you.
TEST 1: Checking The TPS Signal With A Multimeter
This first test checks the throttle position (TP) signal wire on your 4.7L V8 Dodge Ram pickup using a multimeter.
What we'll do here is tap into the sensor's signal wire with the multimeter. On your specific pickup, the wire color depends on the model year:
- 2002–2003: Signal wire is orange with dark blue stripe (ORG/DK BLU).
- 2004–2007: Signal wire is brown with orange stripe (BRN/ORG).
If the TPS sensor is working like it should, you'll see a smooth increase and decrease in voltage as you open and close the throttle plate.
If you don't have a multimeter or need to upgrade yours? This is the one I use and recommend: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (at: amazon.com).
NOTE: The TP sensor must remain connected to its connector to read it's signal. You'll need to either back-probe the connector or pierce the signal wire with a wire-piercing probe. You can see an example and where to buy it here: Wire Piercing Probe.
Let's put this into action:
- 1
Connect the black multimeter test lead to the battery negative (-) post.
- 2
Set your multimeter to Volts DC mode.
- 3
Turn the key to the ON position (engine OFF), but don't crank or start the engine.
This will power up the TP sensor. - 4
Probe the BRN/ORG (or ORG/DK BLU) wire with the red multimeter lead.
This is the TP signal wire and depending on your pickup's model year will either be a BRN/ORG wire or a ORG/DK BLU wire. - 5
With the throttle plate fully closed, you should see 0.3 to 0.9 Volts DC.
This is your base voltage —make a note of it. - 6
Slowly open the throttle plate by hand. You should see the voltage increase steadily as the throttle opens.
- 7
At wide open throttle (WOT), the voltage should read between 3.5 to 4.5 Volts DC.
- 8
Slowly close the throttle plate. The voltage should drop smoothly back down to what you saw in step 5.
Verify that the closed throttle voltage is the same as your starting voltage. - 9
Gently tap the TPS sensor with a screwdriver handle while opening and closing the throttle plate.
NOTE: Tapping the sensor should not affect the voltage readings. If the voltage jumps, cuts out, or glitches, the TPS sensor is faulty and needs to be replaced.
Let's interpret your test result:
CASE 1: The voltage increased and decreased smoothly as you moved the throttle plate. This means the TPS on your 4.7L V8 Dodge Ram pickup is working properly and does not need to be replaced.
CASE 2: The voltage reading did not change or was stuck at one value. This usually means the sensor is dead or the signal wire is shorted.
This kind of issue is often what sets a P0122 (TPS voltage low) or P0123 (TPS voltage high) trouble code.
To make sure the TPS is bad, we now need to confirm that it's getting power. Go to: TEST 2: Making Sure The TPS Is Getting 5 Volts.
CASE 3: The voltage jumped, dropped, or glitched out while tapping the sensor. This is a clear sign that the TPS sensor is internally faulty.
Even if the voltage seems OK when not tapping, any glitchy behavior can trigger a P0121 TPS performance code, or sometimes a P0120 general TPS circuit fault.
If you're seeing one of those codes, and this test confirms a glitch, it's time to replace the TPS sensor.
TEST 2: Making Sure The TPS Is Getting 5 Volts
The throttle position sensor (TPS) on your 4.7L V8 Dodge Ram pickup needs a steady 5 Volt reference to operate correctly.
If this 5 Volt supply is missing, the TPS won't be able to send a proper signal back to the PCM —no matter how good the sensor itself is.
This test checks for the presence of that 5 Volt reference on terminal 1 of the TPS connector:
Let's get this pot of water boiling:
- 1
Disconnect the TPS sensor from its 3-wire connector.
NOTE: We'll be directly testing the female terminals of the connector, not the sensor male terminals. - 2
Turn the key to the ON position (engine OFF) to power up the TPS circuits but don't crank or start the engine.
- 3
Set your multimeter to Volts DC mode.
- 4
Connect the black multimeter test lead to the battery negative (-) post.
- 5
Touch the red multimeter test lead to terminal 1 of the connector.
NOTE: Terminal 1 is the 5 Volt supply wire. It's orange (ORG) on 2002–2003 models, and pink with yellow stripe (PNK/YEL) on 2004–2007 models. - 6
Read the voltage on your meter. You should see somewhere between 4.5 to 5.0 Volts DC.
Let's find out what it all means:
CASE 1: You saw 4.5 to 5.0 Volts DC on terminal 1. That means the PCM is successfully delivering the 5 Volt reference to the TPS sensor and this confirms that the power side of the circuit is doing its job.
Next, you'll test the Ground wire to complete the TPS power circuit check on your 4.7L V8 Dodge Ram pickup. Go to: TEST 3: Making Sure The TPS Is Getting Ground.
CASE 2: You saw 0 Volts. This means the TPS isn't getting any power at all —and that's often what sets a P0122 (TPS low voltage) or P0120 (TPS circuit malfunction) trouble code.
Don't replace the sensor —it's not the problem in this case. Your next step is to check the 5 Volt supply wire for an open-circuit issue between the TPS and the PCM.
Once the 5 Volt reference is restored, the TPS will start working again as it should.
CASE 3: You saw less than 4.5 Volts or an unstable reading. This usually points to a problem in the shared 5 Volt reference circuit —not just the TPS wiring itself.
On your 4.7L V8 Dodge Ram pickup, the 5 Volt supply wire also powers a few other sensors. If one of those sensors suffers an internal electrical failure, it can drag down or distort the 5 Volt supply for the entire circuit —causing all kinds of strange behavior across multiple sensors, including the TPS.
These kinds of voltage issues can confuse the PCM and lead to codes like P0121 or P0123. You'll need to pause TPS testing for now and track down what's interfering with the 5 Volt reference before moving forward.
TEST 3: Making Sure The TPS Is Getting Ground
The TPS on your 4.7L V8 Dodge Ram pickup needs a reliable Ground connection from the PCM to function properly. Without that Ground, the sensor won't be able to send an usable signal —even if it's getting power.
In this test, you'll verify that Ground is present at terminal 3 of the TPS connector by performing a multimeter voltage drop test.
The Ground wire color at terminal 3 will vary depending on your truck's model year:
- 2002–2003: Black with light blue stripe (BLK/LT BLU)
- 2004–2007: Dark blue with dark green stripe (DK BLU/DK GRN)
NOTE: Don't connect the Ground wire directly to battery 12 Volts, or you'll deep fry the PCM. The multimeter voltage test we're about to do is a safe way to check for the presence of Ground in this circuit.
Here's what we need to do:
- 1
Disconnect the TPS sensor from its 3-wire connector.
- 2
Turn the key to the ON position (engine OFF) to power up the circuit.
- 3
Set your multimeter to Volts DC mode.
- 4
Connect the red multimeter test lead to the battery positive (+) post.
- 5
Touch the black multimeter test lead to terminal 3 of the TPS connector.
NOTE: Terminal 3 is the Ground wire. It's black with light blue stripe (BLK/LT BLU) on 2002–2003 models, and dark blue with dark green stripe (DK BLU/DK GRN) on 2004–2007 models. - 6
If Ground is present, you should see 10 to 12 Volts DC on your multimeter's screen.
Alright, let's find out what it all means:
CASE 1: You saw 10 to 12 Volts on your multimeter. That means the TPS Ground circuit is solid and the PCM is providing a good Ground path.
If the sensor is getting its 5 Volt reference (TEST 2 passed), but the signal didn't change during TEST 1, then the TPS itself is definitely bad.
This kind of failure often leads to a P0121 or P0120 trouble code in your 4.7L V8 Dodge Ram pickup, and replacing the TPS should resolve both the signal issue and the stored codes.
If you need to replace the sensor, here are replacements I recommend:
- A-Premium TPS #5017479AA (at: amazon.com).
- Standard Motor Products TH190T Throttle Position Sensor (at: amazon.com).
CASE 2: You saw 0 Volts. That means there's no Ground present at the TPS connector.
This could be due to a damaged Ground wire or an internal fault in the PCM. Without a proper Ground, the TPS won't function at all —and you'll likely see a P0122, P0120, or even a P0123 depending on how the circuit fails.
The sensor isn't the problem— fix the Ground issue first.
CASE 3: You saw an unstable or fluctuating reading. This usually points to a problem in the shared Ground circuit —not just a bad connection at the TPS itself.
On your 4.7L V8 Dodge Ram pickup, the TPS shares its Ground wire with several other sensors. If any of those sensors develop an internal short-circuit, it can cause strange behavior across all the sensors that share this Ground circuit —including the TPS.
This kind of Ground issue can confuse the PCM and trigger codes like P0121 TPS performance or P0123 TPS voltage high.
You'll need to inspect the wiring and rule out the other components on the shared Ground circuit to solve the TP sensor issue on your pickup.
More 4.7L V8 Dodge Ram Pickup Diagnostic Tutorials
I've written quite a few tutorials for the 4.7L V8 Dodge Ram pickup. You can find them in this index:
Here's a small sample of the tutorials you'll find in the index:
- How To Test For A Blown Head Gasket (2002-2009 4.7L V8 Dodge Ram Pickup).
- How To Test The Fuel Injectors (2002-2009 4.7L V8 Dodge Ram Pickup).
- How To Test The CKP Sensor -P0320, P0335, P0339 (2002-2010 4.7L V8 Dodge Ram Pickup).
- How To Check For Vacuum Leaks With Carb Cleaner Spray (2002-2009 4.7L V8 Dodge Ram Pickup).
If this info saved the day, buy me a beer!
