How To Test The TPS With A Multimeter (1994-1995 3.8L Ford Mustang, Ford Thunderbird, Mercury Cougar)

The throttle position sensor (TPS) on the 1994 through 1995 3.8L V6 Ford Mustang is a simple 3 wire component that can be easily test with a multimeter.

In this tutorial I'll show you how to test in a step-by-step manner. With the results of this TPS test you'll be able to find out if it's defective or not.

NOTE: This tutorial applies to the: 1994-1995 3.8L V6 Ford Mustang, 1994-1995 3.8L V6 Ford Thunderbird, and the 1994-1995 3.8L V6 Mercury Cougar.

Contents of this tutorial at a glance:

  1. Symptoms Of A Defective TPS.
  2. TEST 1: Testing The TP Signal With A Multimeter.
  3. TEST 2: Making Sure The TPS Is Getting 5 Volts And Ground.
  4. TPS Trouble Code Won't Go Away.
  5. Where To Buy The TPS And Save.
  6. More 3.8L Ford Tutorials.

NOTE: Starting the 1995 model year, the throttle position sensor was upgraded. It's basically the same TPS as the 1994 model year but with an updated connector. I've included both in the illustration I'm using throughout the tutorial.

En Español You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (1994-1995 3.8L Mustang) (at: autotecnico-online.com).

Symptoms Of A Defective TPS

Since the throttle position sensor plays such an important role in the engine management system that when this bad boy fails, the check engine light will be lit up on your Ford Mustangs instrument panel.

You're also gonna' see that the engines performance is affected. Although not a complete list, you'll see one or more of the following symptoms:

  1. One of the following trouble codes registered in your Ford Mustang fuel injection computer's memory:
    1. 43: Throttle Position (TP) Sensor Below Idle Specification.
    2. 53: Throttle Position (TP) Sensor Above Maximum Voltage.
    3. 63: Throttle Position (TP) Sensor Below Minimum Voltage.
  2. Bad gas mileage.
  3. Lack of power or hesitation when accelerating the engine the vehicle on the road.

TEST 1: Testing The TP Signal With A Multimeter

How To Test The TPS With A Multimeter (1994-1995 3.8L Ford Mustang, Ford Thunderbird, Mercury Cougar)

Before we start testing, let me tell you that when the throttle plate is in its closed position, the TPS will produce a voltage of about 0.5 - 0.9 Volts DC.

As you open the throttle plate, this voltage will increase. So when the throttle plate reaches its maximum open position (called wide open throttle -WOT), the throttle position sensor will produce a voltage of about 4.5 to 4.7 Volts DC.

The wire that transmits the TP signal to the fuel injection computer is the grey with white stripe (GRY/WHT) wire. This wire connects to the terminal identified with the number 2 in the illustration above.

NOTE: To be able to read the TP signal with your multimeter, the throttle position sensor must remain connected to its electrical connector. For this reason you're gonna' need to use a back probe or a wire piercing probe to reach this signal inside the wire. You can see an example of a wire piercing probe here: Wire Piercing Probe.

OK, let's start:

  1. 1

    Place your multimeter in Volts DC mode and connect the red test lead to the GRY/WHT wire of the TP sensor harness connector.

  2. 2

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

  3. 3

    Turn the key on but don't crank or start the engine. This will power up the TPS.

  4. 4

    Manually rotate the throttle.

    You'll get the best results by opening and closing the throttle directly on the throttle body instead of stepping on the accelerator pedal.

  5. 5

    The multimeter should show an increasing voltage as you (or your helper) open up the throttle.

    You'll get the best results by opening and closing the throttle directly on the throttle body instead of stepping on the accelerator pedal.

  6. 6

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

  7. 7

    Using a screwdriver's handle, gently tap the TP sensor as you open and close the throttle and observer the multimeter.

    The purpose (of tapping the TP sensor with the screwdriver's handle) is to see if the TP sensor shows gap's in the voltage signal. 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 take a look at your test results:

CASE 1: The TP signal voltage increased/decreased as you opened/closed the throttle plate. This is the correct test result and let you know that the TPS is working correctly. The TPS itself is not the cause behind the problem on your 3.8L Ford Mustang (or 3.8L Ford Thunderbird or 3.8L Mercury Cougar).

CASE 2: The TP signal voltage had blanks or skips as you opened/closed the throttle plate. This test result let you know that the throttle position sensor is defective.

CASE 3: The TPS voltage signal stayed stuck at one value when you opened/closed the throttle plate. This test result generally tells you that the TP sensor is defective.

To make sure that it is defective, we need to make sure that the TP sensor is getting both power and Ground. For this test go to: TEST 2: Making Sure The TPS Is Getting 5 Volts And Ground.