How To Test The Throttle Position Sensor (2.3L Ranger, Mustang, B2300)

By: Abraham Torres-Arredondo
Created: 10 March 2012
Updated: 19 March 2024
Articl Id: 59

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TEST 3: Testing The Sensor Return (Ground) Circuit

How To Test The Throttle Position Sensor (2.3L Ranger, Mustang, B2300)

The last test in this tutorial, is to check that the PCM is providing a Ground for the throttle position sensor (TPS).

So far in TEST 1, you checked and confirmed that the TPS is not creating a TP signal.

In TEST 2, you have confirmed that the PCM is providing power (5 Volts DC).

Now, we need to verify that the TPS also has a good Ground. Remember, the PCM is the one that provides this Ground internally, so be careful and don't accidentally or intentionally apply power (12 Volts) to this circuit or you'll fry the PCM.

OK, here are the test steps:

1
Place your multimeter in Volts DC mode.
2
Disconnect the TPS from its electrical connector.
3
Turn the key the ON position but don't start the engine.
4
Connect the black multimeter test lead (using the appropriate tool) to the wire labeled with the number 3.
5
Connect the red multimeter test lead to the positive (+) battery terminal.
6
Your multimeter should read 10 to 12 Volts DC.

Let's examine your test results:

CASE 1: The multimeter showed 10 to 12 Volts. This is the correct test result and it tells you that the TPS is getting Ground. You can also conclude that the PCM and the wire/circuit (that supply this Ground) are OK.

This test result also let's you know that the throttle position sensor is bad and needs to be replaced. This conclusion is only true if:

You confirmed in TEST 1 that the TP signal does not increase/decrease as you manually open/close the throttle plate.
You confirmed in TEST 2 that the TPS is getting power (5 Volts).

CASE 2: The multimeter DID NOT show 10 to 12 Volts. Without Ground the TPS will not function.

This test result usually indicates a problem with either the PCM (internal fault/problem) or an open in the wire between the TPS and the PCM itself (and that the TPS itself is not the cause of the problem).

Altho' testing these two conditions are beyond the scope of this article, you have now eliminated the throttle position sensor (TPS) on your Ford vehicle as being the cause of the problem and/or the TPS diagnostic trouble code (DTC) lighting up the check engine light (CEL).

The TPS Code Won't Go Away

So you've tested your Ford (or Mazda) TPS and according to the test results, the TPS is good (or you've already replaced it with a new one), yet the TPS trouble code keeps coming back.

Well, here are a couple of suggestions that might inspire your next diagnostic move:

The throttle plate's idle-stop screw's factory adjustment has been altered (the arrow in the photo above points to it).
- This is usually done so that the engine's idle can be raised to mask a miss/misfire and/or rough idle.
- This increases the TP sensor's signal voltage to the PCM (which the PCM recognizes as being too high). The PCM doesn't like it and lights up the check engine light (CEL).
The throttle cable is binding and causing the throttle plate to not fully close.
- This can be verified by simply having someone inside the vehicle pushing the accelerator pedal to the floor and releasing it, with the engine OFF, while you visually check that the throttle plate and cable are not getting stuck somewhere in their travel.
The TPS is failing intermittently. Which means that it works fine most of the time, but every now and then it doesn't:
- I have found that the best way to test these intermittent problems is to road-test the vehicle with the multimeter hooked up to the TP signal wire with a long wire so that I can comfortably observe the signal going up and down as I or someone else drives.
The TP sensor's connector is bad, usually the locking tab is broken and the connector has worked itself loose, causing an intermittent false connection.