TEST 2: Making Sure The TPS Is Receiving 5 Volts

Making Sure The TPS Is Receiving 5 Volts. How To Test The TPS (1991, 1992, 1993, 1994, 1995 4.0L Ford Ranger And Mazda B4000)

The throttle position sensor needs 5 Volts to function, and the wire that delivers them to it is the brown with white stripe (BRN/WHT) wire of the TP sensor connector.

In the photo above, I've labeled the BRN/WHT wire with the number 1.

In this test section, you'll perform a simple multimeter voltage test to confirm the presence of 5 Volts in the BRN/WHT wire.

If the BRN/WHT wire delivers power to the TPS, your next step is to make sure it's getting Ground.

These are the test steps:

  1. 1

    Select Volts DC mode on your multimeter.

  2. 2

    Disconnect the TP sensor from its connector.

  3. 3

    Probe the brown with white stripe (BRN/WHT) wire with the red multimeter test lead and an appropriate tool (like a wire-piercing probe).

    The BRN/WHT wire is labeled with the number 1 in the photo above.

    NOTE: Be careful not to damage the female terminal.

  4. 4

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

  5. 5

    When everything is set up, have a helper rotate the key to its ON position but don't start the engine.

  6. 6

    The multimeter should display 4.5 to 5 Volts DC.

Let's interpret your test results:

CASE 1: Your multimeter registered 4.5 to 5 Volts. This is the correct and expected test result and it lets you know the TPS is getting power.

Your next and last step is to make sure the TPS is getting Ground. Go to: TEST 3: Making Sure The TPS Is Receiving Ground.

CASE 2: Your multimeter DID NOT register 4.5 to 5 Volts. Double check your connections and make sure that you're testing the correct wire.

If your multimeter still does not register 4.5 to 5 Volts, you can conclude the TPS is not receiving the power it needs to function.

These missing 5 Volts is usually due to an open-circuit problem in the wiring between the TP sensor harness connector and the PCM's harness connector. In the extreme of cases, the PCM has an internal problem (although this is very rare).

Although testing these two conditions is beyond the scope of this tutorial, you have now eliminated the throttle position sensor (TPS) as being the cause of the problem and/or the TP sensor diagnostic trouble code (DTC) lighting up the check engine light (CEL).

TEST 2: Making Sure The TPS Is Receiving Ground

Making Sure The TPS Is Receiving Ground. How To Test The TPS (1991, 1992, 1993, 1994, 1995 4.0L Ford Ranger And Mazda B4000)

So far, your previous two tests have confirmed that:

  • The TP sensor's voltage signal does not increase/decrease when you open/close the throttle plate (TEST 1).
  • The BRN/WHT wire delivers 4.5 to 5 Volts to the TPS (TEST 2).

Your next and last test is to ensure that the gray with red stripe (GRY/RED) wire delivers Ground to the TPS.

In the photo above, I've labeled the GRY/RED wire with the number 3.

You'll confirm or disprove the presence of Ground in the wire with a multimeter voltage test.

CAUTION: The fuel injection computer provides Ground to the TPS internally. Be careful not to pass battery 12 Volts to this wire, or you'll fry the computer. The multimeter voltage test I'm suggesting in the instructions is a safe way to verify the presence of Ground in the wire.

These are the test steps:

  1. 1

    Select Volts DC mode on your multimeter.

  2. 2

    Disconnect the TP sensor from its connector.

  3. 3

    Probe the gray with red stripe (GRY/RED) wire with the black multimeter test lead and an appropriate tool (like a wire-piercing probe).

    The GRY/RED wire is labeled with the number 3 in the photo above.

    NOTE: Be careful not to damage the female terminal.

  4. 4

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

  5. 5

    When everything is set up, have a helper rotate the key to its ON position but don't start the engine.

  6. 6

    The multimeter should display 10 to 12 Volts DC.

Let's interpret your test results:

CASE 1: Your multimeter registered 10 to 12 Volts. This is the correct and expected test result and it lets you know the TPS is getting Ground.

You can conclude that the TPS is bad and needs replacement if you have:

  • Confirmed that the TP sensor is not producing a voltage signal that increases/decreases when you open/close the throttle plate (TEST 1).
  • Confirmed that the TP sensor is receiving 4.5 to 5 Volts (TEST 2).
  • Confirmed that the TP sensor is receiving Ground (this test section).

CASE 2: Your multimeter DID NOT register 10 to 12 Volts. Double check your connections and make sure that you're testing the correct wire.

If your multimeter still does not register 10 to 12 Volts, you can conclude the TPS is not receiving the Ground it needs to function.

This missing Ground is usually due to an open-circuit problem in the wiring between the TP sensor harness connector and the PCM's harness connector. In the extreme of cases, the PCM has an internal problem (although this is very rare).

Although testing these two conditions is beyond the scope of this article, you have now eliminated the throttle position sensor (TPS) as being the cause of the problem and/or the TP sensor diagnostic trouble code (DTC) lighting up the check engine light (CEL).

More 4.0L Ford Ranger (Mazda B4000) Tutorials

You can find a complete list of 4.0L Ford Ranger (Mazda B4000) tutorials in this index:

Here's a small sample of the tutorials you'll find in the index:

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Ford Vehicles:

  • Ranger 4.0L
    • 1990, 1991, 1992, 1993, 1994

Mazda Vehicles:

  • B4000 4.0L
    • 1994
  • Navajo 4.0L
    • 1991, 1992, 1993, 1994