How To Test the Throttle Position Sensor (TPS) -2.3L Ford

The most accurate way to test the throttle position sensor (TPS) on your 2.3L Ford Ranger (Mustang, Mazda B2300) is with a multimeter.

In this tutorial, I'll show you where you need to make your multimeter connections to test it and find out if its bad (or not) and in the process troubleshoot the following diagnostic trouble codes:

  1. P0121: Throttle Position Sensor Performance Problem.
  2. P0122: Throttle Position Sensor Circuit Low Input.
  3. P0123: Throttle Position Sensor Circuit High Input.
  4. P1121: Throttle Position Sensor Inconsistent with Mass Air Flow.
  5. P1124: Throttle Position Sensor out of Self-Test Range.
  6. P1125: Throttle Position Sensor Intermittent.

Here are the contents of this tutorial at a glance:

  1. Basics of the Throttle Position Sensor (TPS).
  2. TEST 1: Checking the Throttle Position Sensor (TPS) Signal.
  3. TEST 2: Checking Throttle Position Sensor (TPS) Power and Ground.
  4. Throttle Position Sensor (TPS) is Good But Code Won't Go Away.
  5. Where to Buy the TP Sensor and Save Some $$$.
  6. More ‘How To Test’ Tutorials.

En Español You can find this tutorial in Spanish here: Cómo Probar el Sensor TPS (1995-1997 2.3L Ford) (at: autotecnico-online.com).

To test the older style TPS (1994 and older), take a look at this tutorial: How to Test the Throttle Position Sensor (2.3L Ranger, Mustang, B2300) (at: easyautodiagnostics.com).

Basics of the Throttle Position Sensor (TPS)

How To Test the Throttle Position Sensor (TPS) -2.3L Ford

As you're probably already aware, the throttle position sensor on your 2.3L Ford has 3 wires coming out of its harness connector.

To test the throttle position sensor, we need to know which wire (of the TP sensor harness connector) provides power, which one provides ground and which one is the one that carries the throttle position signal to your Ford's PCM.

Using the illustration (in the image viewer) of the front of the TP sensor engine harness connector, I'll briefly go over each one.

Ford Ranger and Mazda B2300 TP Sensor Circuits
(1995, 1996, 1997 2.3L)
Pin Wire Color Description
1 Brown w/ White stripe 5 Volt Reference
2 Gray w/ White stripe Throttle Position Signal
3 Gray w/ Red stripe Ground

TEST 1: Checking the
Throttle Position Sensor (TPS) Signal

Checking the Throttle Position Sensor (TPS) Signal With a Multimeter. How To Test the Throttle Position Sensor (TPS) -2.3L Ford

The key to diagnosing the throttle position sensor on your 2.3L Ford is to know that as the throttle plate opens, the voltage output of the TP sensor increases. As the throttle plate closes, the voltage output of the sensor decreases.

So, you and I will tap into the middle wire of the TP sensor harness connector (this is the gray w/ white stripe wire) with a multimeter and manually open and close the throttle plate... to see if the TP sensor's voltage output increases and decreases accordingly.

IMPORTANT: Remember this is an on car test of the sensor, even though some of the images of the TPS show it off of the engine, so don't remove the TPS to test it.

Here are the test steps:

  1. 1

    Place your multimeter in Volts DC mode and connect the red test lead to the wire that connects to circuit #2 of the TPS connector..

    This is the Gray w/ White stripe wire of the TP sensor harness connector of your 2.3L Ford.

    NOTE: The TP sensor connector needs to be connected to the TPS, so you'll need to either back-probe the connector or use a wire piercing probe to get to the signal inside the wire (to see what a wire piercing probe looks like: Wire Piercing Probe Tool).

  2. 2

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

  3. 3

    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.

  4. 4

    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.

  5. 5

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

  6. 6

    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 what your test results mean:

CASE 1: The TP sensor signal's voltage increased and decreased smoothly and without gaps. This is the correct and expected TPS test result. This result tells you that the TPS is working correctly.

This test result also tells you that:

  1. Circuit #1 is providing ground.
  2. Circuit #3 is providing power (5 Volts).

CASE 2: The TP sensor signal's voltage did not increase or decrease. In the majority of the cases this TPS result tells you that the sensor is bad. But not always.

To be sure that the TPS is truly fried, we need to do 2 more tests. These tests involve checking that the sensor is getting both power and ground. For these tests, go to TEST 2: Checking Throttle Position Sensor (TPS) Power and Ground.

CASE 3: The TP sensor signal's voltage showed gaps in its voltage output as you tapped the sensor with the screwdriver. If the gaps in the multimeter's voltage readings only showed up when you were tapping on the TPS (with the screwdriver's handle) then this test result tells you that the TPS is bad and needs to be replaced.