How To Test The TPS (1997-2003 5.2L, 5.9L V8 Dodge Ram Pickup)

The throttle position sensor (TPS) can be easily tested using only a multimeter and in this article, I'll show you how.

This article covers troubleshooting diagnostic trouble codes (DTCs) P0121, P0122, P0123 on the 5.2L and 5.9L Dodge Ram pickup.

NOTE: This tutorial only covers the throttle position sensor on the 1997 thru' 2003 Dodge Ram pickup. For the 1992-1996 Dodge Ram pickup, see the following tutorial:

• How To Test The TPS (1992-1996 5.2L, 5.9L Dodge Ram Pickup).

You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (Chrysler 3.9L, 5.2L, 5.9L) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles (since they use the exact same throttle position sensor):

• Dodge Ram 1500 Pickup 5.2L V8: 1997, 1998, 1999, 2000, 2001.
• Dodge Ram 2500 Pickup 5.2L V8: 1997, 1998.
• Dodge Ram 1500 Pickup 5.9L V8: 1997, 1998, 1999, 2000, 2001, 2002, 2003.
• Dodge Ram 2500 Pickup 5.9L V8: 1997, 1998, 1999, 2000, 2001, 2002.
• Dodge Ram 3500 Pickup 5.9L V8: 1997, 1998, 1999, 2000, 2001, 2002, 2003.

3.9L V6 Dodge Ram Pickup TPS Tests:

• How To Test The TPS (1997-2003 3.9L V6 Dodge Ram Pickup).

3.9L V6 Dodge Ram Van TPS Tests:

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

5.2L, 5.9L V8 Dodge Ram Van TPS Tests:

• How To Test The TPS (1997-2003 5.2L, 5.9L V8 Dodge Ram Van).

All V8 Dodge Ram Pickup TPS Sensor Test Tutorials:

• How To Test The TPS (1989-1990 5.2L, 5.9L V8 Dodge Ram Pickup).
• How To Test The TPS (1991 5.2L, 5.9L V8 Dodge Ram Pickup).
• How To Test The TPS (1992-1996 5.2L, 5.9L V8 Dodge Ram Pickup).

The following wiring diagram may come in handy:

• 1996-1998 TP Sensor Circuit Diagram (Dodge 3.9L, 5.2L, 5.9L).

Symptoms Of A Bad TPS

You'll have the check engine light on your instrument cluster shining nice and bright for sure.

You'll also experience one or several of the following symptoms:

• TPS diagnostic trouble codes (DTCs): One of the following DTCs is illuminating the check engine light:
  • P0121: TPS Voltage Does Not Agree with MAP.
  • P0122: Throttle Position Sensor Voltage Low.
  • P0123: Throttle Position Sensor Voltage High.
• Bad gas mileage: You know that it's not the price of gasoline that has you thinking that your pickup is costing you more at the pump.
• No power: When you step on the gas, either to accelerate from a start or already cruising on the highway, the engine just doesn't respond like it used to.
• Engine hesitation: Hesitation as you accelerate the vehicle. It feels like all of a sudden someone cut the power out momentarily as you step on the gas to get the vehicle moving.
• Engine no-start: You can spend all day cranking the engine, but it won't start.

How The Throttle Position Sensor Works

The throttle position sensor's job is to measure the angle of the throttle. So here, in a nutshell, is how the throttle position sensor works when you crank and start your 5.2L, 5.9L Dodge:

• TPS enabled: The fuel injection computer supplies 5 Volts and Ground to the throttle position sensor.
  • 5 Volts is provided by the wire labeled with the number 3.
  • Ground is provided by the wire labeled with the number 1.
• Throttle fully closed: Now, since the throttle is closed, the TPS (with power and Ground supplied) sends the PCM (Powertrain Control Module=Fuel Injection Computer) a DC voltage signal of about 0.3 to 0.9 Volt. This value is what the PCM associates with a closed throttle.
  • The TP signal is sent to the PCM by the wire labeled with the number 2.
• Throttle begins to open: Once you throw your pickup in drive and accelerate, the throttle opens:
  • The throttle position sensor immediately sends this change of the throttle angle as an increasing voltage signal to the PCM.
  • With this increasing voltage signal, the PCM knows it's time to inject more fuel, advance ignition timing, and a host of other things it has to do to keep your V8 Dodge Ram pickup running optimally.
• Wide Open Throttle (WOT): At maximum throttle, the sensor should read close to 4.5 Volts DC.
• Throttle closing again: As you let go off the accelerator pedal to slow down, the throttle plate closes and of course the TP sensor sends the info to the PCM as it returns to its base voltage signal, till the whole cycle begins again.

Pretty easy stuff? The cool thing is that the tests to check out the TP sensor's performance are as easy too. Since testing the TPS simply involves making sure that the sensor is creating a throttle angle voltage signal (which can be verified with a multimeter in Volts DC mode).

If the TP sensor is not creating a voltage signal, then the next steps are to make sure that it's getting power and Ground from the PCM. These two things you can also verify with your multimeter.

IMPORTANT: Since you'll be working in the engine compartment take all necessary safety precautions and use common sense.

Where To Buy The TPS And Save

You can buy the throttle position sensor for your 5.2L, 5.9L V8 Dodge Ram pickup in just about any auto parts store (but it'll cost a whole lot more).

My suggestion is to buy it online or at least comparison shop to get an idea of how much it costs and how much you can save.

Not sure if the above throttle position sensor (TPS) fits your particular Dodge Ram pickup? Don't worry, once you get to the site, they'll make sure it fits by asking you the particulars of your vehicle. If it doesn't fit, they'll find you the right one.

TPS TEST 1: Testing The TPS Signal

The first order of business, is to test the throttle position voltage signal right off the bat with your multimeter in Volts DC mode.

What we're looking for, if the TPS is good, is for the TPS signal to increase/decrease as the throttle plate opens/closes.

Depending on your TPS voltage signal test result, you'll be able to conclude the TPS is good or continue on to the next tests.

NOTE: It's best to test the throttle position sensor (TPS) with the engine warmed up. This will increase the accuracy of your test result, especially if the TP sensor is failing intermittently.

OK, let's start:

1. 1

   Ground the black multimeter test lead directly on the battery negative (-) post.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

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

4. 4

   Connect the red test lead to the ORG/DK BLU of the TP sensor harness connector.
   
   NOTE: The TP sensor connector needs to be connected to the TPS, so you'll need to either back-probe the connector or use a wire piercing probe to get to the signal inside the wire (to see what a wire piercing probe looks like: Wire Piercing Probe Tool).

5. 5

   At this point (with the throttle plate closed) your multimeter should read a voltage between 0.3 to 1.0 Volts DC.

6. 6

   Manually open the throttle plate from the engine compartment.
   
   NOTE: You'll get the best results by opening and closing the throttle directly on the throttle body instead of stepping on the accelerator pedal.

7. 7

   The multimeter should show an increasing voltage as you (or your helper) open up the throttle.
   
   With the throttle plate completely open, your multimeter should read: 3.2 to 4.9 Volts DC.

8. 8

   Slowly close the throttle plate again.

9. 9

   The multimeter should show a decreasing voltage as you begin to close the throttle.

10. 10

    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's voltage signal glitches out (shows gaps in the reading). 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 examine your test result:

CASE 1: The multimeter registered a smooth increase or decrease in voltage with no gaps. This tells you that the throttle position sensor itself is OK and not causing the issue you're trying to troubleshoot.

Now, if the throttle position sensor code won't go away, take a look at the info found at: TPS Code Won't Go Away for a few more suggestions as to what could be causing the TPS diagnostic trouble code (DTC).

CASE 2: The TPS voltage stayed stuck 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: TPS TEST 2: Making Sure The TPS Is Getting 5 Volts.

CASE 3: The multimeter DID NOT register any voltage. This test result doesn't condemn the TPS as bad just yet. We need to rule out the possibility that the TPS may be missing either power or Ground.

The next step (and the next test) is to make sure the throttle position sensor (TPS) is getting power, go to: TPS TEST 2: Making Sure The TPS Is Getting 5 Volts.

CASE 4: The voltage reading glitched out when tapping the TPS. This means that the throttle position sensor (TPS) is bad. Replace the throttle position sensor.