How To Test The TPS (1998, 1999, 2000, 2001 2.5L Ford Ranger And Mazda B2500)

The throttle position sensor (TPS) on the 1998, 1999, 2000, and 2001 2.5L Ford Ranger (Mazda B2500) pickup truck is a simple 3-wire component.

It can be easily tested with a simple multimeter and that's how I'll show you how to test it in this tutorial.

With the results of this TPS multimeter test, you'll be able to accurately diagnose it as defective (or not).

Symptoms Of A Defective TPS

When the throttle position sensor fails, the thing that you're gonna' notice is the check engine light shining nice and bright on your Ford Ranger's instrument cluster. The check engine light is going to be lit by one of the following trouble codes:

  1. P0121: TPS Circuit Performance Problem.
  2. P0122: TPS Circuit Low Input.
  3. P0123: TPS Circuit High Input.
  4. P1120: TPS Out Of Ranger.
  5. P1121: TPS Inconsistent With MAF Sensor.
  6. P1124: TPS Out Of Self-Test Range.
  7. P1125: TPS Intermitten.

But a TPS trouble code lighting up the check engine light isn't the only symptom that you're going to see. You'll see one or several of the following:

  1. Bad gas mileage.
  2. Erratic shifting from the automatic transmission.
  3. Lack of power as you exit the vehicle on the road.
  4. The motor jerks (hesitates) when you step on the accelerator (when you're driving down the road).

TEST 1: Testing The TPS Signal With A Multimeter

Testing The TPS Signal With A Multimeter. How To Test The TPS (1998, 1999, 2000, 2001 2.5L Ford Ranger And Mazda B2500)

In a nutshell the TPS is designed to measure the throttle plate angle as it opens and closes.

In it's closed position, the TP sensor produces a voltage signal of about 0.2 to 0.5 volt DC.

This voltage signal increases as the throttle plate opens. When the throttle plate opens to its maximum open position, the voltage signal will be about 4.2 to 4.5 volt DC.

The really cool thing, that you and I can test to see if this voltage signal increases/decreases as we open/close the throttle plate. We don't even need to remove the throttle position sensor to do it.

We'll accomplish this by connecting our multimeter to the grey with white stripe (GRY/WHT) wire of the TP sensor's electrical connector (see photo above).

NOTE: The TPS must remain connected to its electrical connector to perform the TPS signal test. You'll need to use a back-probe or a wiring-piercing-probe to test the signal. You can take a look at this tool here: Wire Piercing Probe Review (Power Probe PWPPPPP01).

These are the test steps:

  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 TP signal test result:

CASE 1: The TP signal voltage increased/decreased as you manually opened/closed the throttle plate. This is the correct test result and let you know that the throttle position sensor is functioning correctly.

CASE 2: The TP signal voltage DID NOT increase/decrease as you manually opened/closed the throttle plate. This test result usually lets you know that the throttle position sensor is defective.

Before you run out and buy it, I recommend that you make sure that the TP sensor is getting power and Ground. With this in mind, continue on to the next test: TEST 2: Making Sure The TPS Is Getting 5 Volts.