TPS TEST 1: Testing The TPS Signal

How To Test The TPS (Dodge 3.9L, 5.2L, 5.9L)

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

Depending on your TPS voltage signal test result, you'll be able to condemn the TP sensor as BAD or continue on to the next tests.

I've divided the test into three parts. To accomplish the steps in PART 3, you'll need a helper.

NOTE: One last thing: 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:

Part 1

  1. 1

    Select Volts DC mode on your multimeter and with the RED multimeter lead probe the wire labeled with the number 2 in the photos. This is the circuit that supplies the TP signal to the PCM.

    The throttle position sensor, must be connected to its electrical connector during this test.

    NOTE: Since the TP sensor must remain connected to its connector for this test to work, you'll need to a tool like a back-probe or a wire-piercing to tool. You can find out what a wire-piercing tool looks like and how it's used here: Wire Piercing Probe Tool Review (Power Probe PWPPPPP01).

  2. 2

    Ground the BLACK multimeter test lead on the battery negative terminal. Have you helper turn the key On, but don't start the engine (this will power up the TP sensor).

  3. 3

    With the Key On and the Engine Off (KOEO), you should see .5 to .9 Volts DC on your multimeter. If you don't, don't worry about it just yet, continue with the other steps.

Part 2

  1. 4

    Now, slowly open the throttle (by hand and from the engine compartment) while you observe the change in voltage numbers on your multimeter.

    For this test result to be accurate, you need to open the throttle by hand and not from inside the vehicle.

  2. 5

    As the throttle opens, the voltage numbers will increase. This increase in voltage should be smooth and without any gaps or skips. Once the throttle is wide open, your multimeter should read somewhere between 3.5 to 4.9 Volts DC.

  3. 6

    Now, slowly close the throttle. As the throttle is closing, you should see the voltage decrease smoothly and without any gaps or skips, to the exact same voltage you noticed in step 4.

Part 3

  1. 7

    OK, now you'll need someone to help you lightly tap on the throttle position sensor with the handle of a screw-driver (or something similar, and I want to emphasize the words ‘lightly tap’) as you slowly open and close the throttle and observe the multimeter.

    If the TPS is bad, the tapping will cause the voltage numbers to skip or go blank. If the TPS is OK, the tapping will have no effect on the voltage numbers.

  2. 8

    Repeat step 7 several times to make sure of your multimeter test results.

Interpreting The Results

CASE 1: If 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 Will Not Go Away for a few more suggestions as to what could be causing the TPS diagnostic trouble code (DTC).

CASE 2: If the multimeter DID NOT register a smooth increase or decrease in voltage, and you saw the voltage reading skip or go dead when tapping the TPS... then this means that the throttle position sensor (TPS) is BAD. Replace the throttle position sensor.

CASE 3: If 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: Testing The 5 Volt Reference Signal.