How To Test The TPS (1997-2003 3.9L Dodge Ram 1500 Pickup/Van)

TEST 2: Making Sure The TPS Is Getting 5 Volts

As I mentioned before, the throttle position sensor needs 5 Volts and Ground to create its TPS voltage signal.

So if in TEST 1 the TPS is not creating an increasing/decreasing voltage signal (as you open/close the throttle plate), then there's a good chance it might be missing 5 Volts.

On the 1997-2001 3.9L V6 Dodge Ram 1500 Pickup and 1997 Dodge Ram 1500 Van, the wire that supplies these 5 Volts is the violet with white stripe (VIO/WHT) wire labeled with the number 3 in photo 1 of 2 above.

On the 1999-2003 3.9L V6 Dodge Ram 1500 Van, the wire that supplies these 5 Volts is the orange (ORG) wire labeled with the number 3 in photo 2 of 2 above.

NOTE: Avoid probing the front of the female terminal with your multimeter test lead. Use a back probe or a wire piercing probe instead.

Let's get testing:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

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

3. 3

   Disconnect the TPS from its electrical connector.

4. 4

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

5. 5

   With the red multimeter test lead and an appropriate tool probe the wire labeled with the number 3 in the photo above.

6. 6

   The multimeter should display 4.5 to 5 Volts.

Let's analyze your test result:

CASE 1: The multimeter registered 4.5 to 5 Volts. This is the correct test result and confirms that the fuel injection computer and the wire are supplying the TPS with power.

The next step is to test the Ground wire of the throttle position sensor, go to:TEST 3: Making Sure The TPS Is Getting Ground.

CASE 2: The multimeter DID NOT register 4.5 to 5 Volts. This test result confirms that the TPS is not getting power.

The two most likely reasons for this are: 1) an open-circuit problem in the wire or 2) the PCM may be fried.

Altho' it's beyond the scope of this tutorial to test these two conditions, you have now eliminated the throttle position sensor (TPS) on your 3.9L Dodge as being the cause of the problem and/or the TPS diagnostic trouble code (DTC) lighting up the check engine light (CEL).

TEST 3: Making Sure The TPS Is Getting Ground

So far your TPS test results have confirmed that:

• A TPS failure code is lighting up the check engine light (CEL) on your Dodge's instrument cluster.
• The TPS is not creating a TPS voltage signal that increases/decreases as you open/close the throttle plate.
• The TPS is getting 5 Volts DC.

The last test, before condemning the throttle position sensor as bad, is to verify that it's getting Ground.

The wire that we're gonna' test, for the presence of Ground, is the black with light blue stripe (BLK/LT BLU) wire of the connector.

In the photo above, this wire is labeled with the number 1.

IMPORTANT: The PCM is the one that provides this Ground internally, so be careful and don't accidentally or intentionally apply power (12 Volts) to this wire or you'll fry the PCM.

OK, here are the test steps:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

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

3. 3

   Disconnect the TPS from its electrical connector.

4. 4

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

5. 5

   With the black multimeter test lead and an appropriate tool probe the wire labeled with the number 1 in the photo above.

6. 6

   The multimeter should display 10 to 12 Volts.

Let's take a look at your test results:

CASE 1: The multimeter showed 10 to 12 Volts. This is the correct test result and tells you that the TPS is getting Ground.

This multimeter test result also confirms that the TPS sensor is bad and needs to be replaced if you have:

1. Confirmed that the TPS is not creating an increasing/decreasing voltage signal when you open/close the throttle plate TEST 1.
2. Confirmed that the TP sensor is getting 5 Volts (TEST 2).
3. In this test section, you have confirmed that the TP sensor is receiving Ground.

If you'd like to save some bucks on the TP sensor, consult my recommendations here: Where To Buy The TPS And Save.

CASE 2: The multimeter DID NOT show 10 to 12 Volts. Without Ground the throttle position sensor will not create its TPS signal.

This test result usually indicates a problem with either the PCM (internal fault/problem) or an open-circuit problem in the wire between the TPS and the PCM itself.

Altho' testing these two conditions are beyond the scope of this tutorial, you have now eliminated the throttle position sensor (TPS) on your 3.9L Dodge Ram 1500 Pickup/Van as being the cause of the problem and/or the TPS diagnostic trouble code (DTC) lighting up the check engine light (CEL).

TPS Code Won't Go Away

In some cases, even though the TPS is good (or new), the check engine light keeps coming back on after you have erased the diagnostic trouble code (DTC) from the computer's memory. Well, here are a couple of suggestions that might inspire your next diagnostic move:

1. The throttle plate's idle-stop screw's factory adjustment has been altered. This is usually done to increase the engine's RPM at idle to mask a rough idle problem. This increases the TP sensor's signal to the PCM. The PCM doesn't like it and light ups the check engine light (CEL).
2. The throttle cable is binding and causing the throttle plate to not fully close.
   
   This can be verified by simply having someone inside the vehicle pushing the accelerator pedal to the floor and releasing it, with the engine OFF, while you visually check that the throttle plate and cable are not getting stuck somewhere in their travel.
3. The TPS is failing intermittently. Which means that it works fine most of the time, but every now and then it doesn't:
   
   I have found that the best way to test these intermittents is to road-test the vehicle with the multimeter hooked up to the TP signal wire with a long wire so that I can comfortably observe the signal going up and down as I or someone else drives.
4. The TP sensor's connector is bad, usually the locking tab is broken and the connector has worked itself loose, causing an intermittent false connection.

More 3.9L V6 Dodge Tutorials

I've written quite a few 3.9L V6 Dodge ‘how to’ tutorials that may help you troubleshoot the issues on your Dodge van, pick up or SUV. You can find all in these two indexes:

• 3.9L Dodge Index Of Articles.
• 3.9L, 5.2L, 5.9L Dodge Index Of Articles.

Here's a small sample of the articles/tutorials you'll find in the indexes:

• How To Test A No Start Condition (Dodge 3.9L, 5.2L, 5.9L).
• How To Diagnose Misfire Codes (Dodge 3.9L, 5.2L, 5.9L).
• How To Test The Fuel Injectors (Dodge 3.9L, 5.2L, 5.9L).
• How To Test The Ignition Coil -No Start Tests (Chrysler 3.9L, 5.2L, 5.9L).
• How To Test The MAP Sensor (P0107, P0108) (Dodge 3.9L, 5.2L, 5.9L).