How To Test The Throttle Position Sensor (2001-2007 3.0L Ford Escape)

The throttle position sensor (TPS) on your 3.0L V6 Ford Escape and Mazda Tribute can be easily tested with a multimeter.

Although a scan tool is a "must" tool to have, no scan tool is required to troubleshoot and diagnose the TPS and I'll show you how to do it step by step.

I've also included some important do's and don'ts to make your diagnostic as easy and as uncomplicated as possible.

You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS Con Multímetro (2001-2007 3.0L Ford Escape) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 3.0L Ford Escape: 2001, 2002, 2003, 2004, 2005, 2006, 2007
• 3.0L Mazda Tribute: 2001, 2002, 2003, 2004, 2005, 2006, 2007

Symptoms Of A Bad Escape (Tribute) TPS

Beside the check engine light (CEL) being on and driving you nuts, here are some other symptoms your Ford Escape or Mazda Tribute may be experiencing:

1. TPS diagnostic trouble codes (DTCs) stored in the vehicle's computer's memory.
   • P0121: Throttle Position (TP) Circuit Performance Problem.
   • P0122: Throttle Position (TP) Circuit Low Input.
   • P0123: Throttle Position (TP) Circuit High Input.
2. Really bad gas mileage.
3. Transmission does not shift out of second gear.
4. No power as you accelerate the vehicle.
5. Hesitation when you step on the accelerator pedal.

What Tools Do I Need?

To test the throttle position sensor you don't need any expensive testing equipment or tools, just a simple multimeter will do to be able to use the info in this article (don't have a digital multimeter? Need to buy one? Click here to see my recommendation:

• Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (Amazon affiliate link).

You may need a helper to perform some of these tests.

Circuit Descriptions Of The Ford Escape (Tribute) TPS

There are three wires sticking out of the Ford Escape (and Mazda Tribute) throttle position sensor (TPS). Each wire provides a specific type of signal to the TPS or to the PCM (Powertrain Control Module=Fuel Injection Computer). Below are the circuit descriptions of each.

• Circuit labeled 1:
  • Sensor Return (Ground) Circuit.
• Circuit labeled 2:
  • Throttle Position (TP) Signal Circuit.
• Circuit labeled 3:
  • 5 Volts from PCM.

I'm gonna' make one very important recommendation to you when testing the signals of each wire. And that is to avoid probing the front of the female terminal of the TPS connector with the multimeter test leads. It's best to use a back probe or a wire-piercing probe (you can see what one looks like here: Wire Piercing Probe) to get to and test the signal.

One last observation, these three circuits go directly to the PCM. So you need to be careful not to short these wires to power (12 Volts) or you may fry the PCM.

How Does The Ford Escape (Mazda Tribute) TPS Work?

Here's some very basic working theory that'll help you to understand the 'why' and 'how' of the three tests you're gonna' do with the help of this article. OK, in a nutshell, when you crank and start your Ford vehicle:

1. The throttle position sensor gets 5 Volts and Ground from the PCM.
2. Once the car starts and is idling, the TPS sends a base throttle position signal of about 0.9 to 1 Volt to the PCM.
3. Once you step on the accelerator pedal to start moving the car, the TP sensor starts to measure the amount of throttle plate opening (caused by your foot) into a rising voltage signal the PCM uses to calculate fuel injection, ignition timing, transmission shift points, etc.
4. As you let go off the gas pedal (accelerator pedal), the TP sensor decreases the voltage signal to the PCM and returns to its base voltage signal, till you step on the accelerator pedal to move the vehicle and the cycle begins again.

Pretty simple stuff, no? Well testing it is just as simple. Since you'll be working in the engine compartment, no need to tell you (but I'm gonna' tell you anyway) to be alert and be very careful. Use common sense and take all necessary safety precautions. OK, let's get this show on the road! Go to: TEST 1: Making Sure The TPS Is Getting 5 Volts.

Where To Buy The TPS And Save

The following links will help you comparison shop for the throttle position sensor. If the locking tab, on the TPS connector has broken, you can buy it online too. I have included a link where you can buy it below:

TEST 1: Making Sure The TPS Is Getting 5 Volts

The first thing that we're gonna' do is to make sure that the TPS is getting 5 Volts DC from the fuel injection computer.

If 5 Volts are present, then the next step is to make sure that the TPS is getting Ground (TEST 2).

Although all of the TPS tests are done with the engine off, it's important that your Ford Escape or Mazda Tribute's engine be at normal operating temperature for the tests.

These are the test steps:

1. 1

   Once you have warmed up the engine, turn it off and remove any plastic covers that may be hiding the TPS from view and access.

2. 2

   If necessary, remove the air duct that connects the throttle body to the mass air flow sensor assembly.

3. 3

   Put your multimeter in Volts DC mode.
   
   If you don't have a digital multimeter and need to buy one, see my recommendation here: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (Amazon affiliate link).

4. 4

   Disconnect the TPS from its electrical connector.

5. 5

   With the red multimeter test lead, and an appropriate tool, probe the wire labeled with the number 3 in the photo above.

6. 6

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

7. 7

   Turn the key to its ON position but do not start the engine.
   
   Your multimeter should read 4.5 to 5 Volts.

Let's take a look at what your test results mean:

CASE 1: The multimeter registered 4.5 to 5 Volts. This is the correct test result.

So far so good, since this confirms that the PCM is providing the correct voltage to the TPS. The next step is to test the Signal Return Circuit. For this test go to: TEST 2: Making Sure The TPS Is Getting Ground.

CASE 2: The multimeter DID NOT register 4.5 to 5 Volts. This test result lets you know that the fuel injection computer is NOT providing the voltage that the TPS needs to operate.

This missing voltage could be the result of an open-circuit problem in the wire or the PCM may be fried.

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).

TEST 2: Making Sure The TPS Is Getting Ground

In this test step, you're gonna' verify that the PCM is or is not providing a Ground for the 5 Volts you verified that the TPS is receiving in TEST 1.

The wire that supplies Ground to the TPS, of your 2001-2007 3.0L Ford Escape (Mazda Tribute), is the one labeled with the number 1 in the photo above.

NOTE: The fuel injection computer is the one that supplies Ground to the TPS. Be careful and don't short the Ground wire to battery 12 Volts or you'll damage the computer. The multimeter voltage test suggested in the test steps is a safe way to test for the presence of Ground in the wire.

OK, let's start:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Disconnect the TPS from its electrical connector.

3. 3

   Probe the wire labeled with the number 1 in the photo above, with the black multimeter test lead and the appropriate tool.

4. 4

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

5. 5

   Turn the key to its ON position but don't start the engine.
   
   The multimeter should display 10 to 12 Volts if Ground is present.

Let's take a look at what your test results mean:

CASE 1: The multimeter displayed 10 to 12 Volts. This is the correct test result and lets you know that the PCM is feeding a good Ground to the TP sensor.

The next step is to verify that the TP sensor is creating a good throttle position signal the PCM can use, go to: TEST 3: Testing The TP Signal.

CASE 2: The multimeter DID NOT display 10 to 12 Volts. Then the PCM is NOT supplying a Ground either because of an internal fault/problem or there's an open-circuit problem in the wire between the TPS and the PCM itself.

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).

TEST 3: Testing The TP Signal

Up until this point, your tests have verified that the throttle position sensor is being supplied with 5 Volts and Ground. The next step is to see if it's producing a good signal that the PCM can use.

If the throttle position sensor (TPS) is working correctly, the multimeter will register a smooth increase in the DC voltage until the maximum voltage is reached, which is about 4.5 Volts DC.

Then, as you slowly release the throttle plate back to its closed position, the multimeter will display a gradual decrease in voltage till the initial base voltage is achieved (which you recorded in the beginning of the test).

If the TPS is bad, the voltage reading will stay stuck in one value or the voltage signal will have gaps as you open/close the throttle plate.

You'll need a helper to assist you in this test step, since he or she will need to lightly tap on the throttle position sensor's body with a screw driver (or other appropriate tool) while you observe the multimeter and manually actuate the throttle plate.

NOTE: To test the TPS voltage signal, the throttle position sensor must remain connected to its electrical connector. You'll need to use a back probe or a wire piercing probe to test for the TPS signal. You can see an example of this tool here: Wire Piercing Probe.

OK, let's start testing:

Part 1

1. 1

   Select Volts DC mode on your multimeter and reconnect the TPS to its electrical connector.

2. 2

   Probe the circuit labeled with the number 2 in the photo with the red multimeter test lead, using an appropriate tool.

3. 3

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

4. 4

   Turn the key ON with the engine OFF.
   
   Your multimeter should register about 0.9 to 1 Volt (this voltage specification might vary about ± 1 volt on your Escape or Tribute).

Part 2

1. 5

   Manually rotate the throttle plate by hand as you eye-ball the multimeter's voltage readings.

2. 6

   The multimeter's initial voltage reading should increase smoothly as you open the throttle plate to its wide open position (WOT).

3. 7

   Now, slowly release the throttle plate to its fully closed position, all the while observing the multimeter's reading.
   
   The multimeter's voltage reading should decrease in a smooth and linear fashion.

Part 3

1. 8

   OK, now have your helper lightly tap the TP sensor with the butt of a screw-driver's handle (or something similar).

2. 9

   As he or she taps, you need to slowly and smoothly open the throttle to its wide open position and then slowly release it back to its closed position.
   
   All the while you've got your eyes glued on the multimeter to see if the tapping affects the voltage readings. Repeat this (tapping the throttle position sensor) several times to make sure of your results.

Let's examine your test result:

CASE 1: The multimeter registered a smooth increase or decrease in voltage. This is the correct test result and tells you that the TP sensor is working OK and is not the cause of the TPS fault code issue.

If the TPS trouble code keeps coming back, check out the suggestions here: The TPS Code Won't Go Away as to what could be causing the TPS diagnostic trouble code (DTC).

CASE 2: The multimeter DID NOT register a smooth increase or decrease in voltage. This test result tells you that the throttle position is bad only if you have:

• Confirmed that the TPS is getting 5 Volts DC.
• Confirmed that the TPS is getting Ground.
• Confirmed the TPS is not producing a voltage signal that increases/decreases as you open/close the throttle plate.

The TPS Code Won't Go Away

So you've tested the TPS per the instructions in this article and according to the test results, the TPS is good, yet the check engine light is still on. Well, here are a couple of suggestions that might inspire your next diagnostic move:

1. The throttle plate's idle-stop screw's factory adjustment has been altered so that the engine could be idled up and mask a miss/misfire and/or rough idle. This increases the TP sensor's signal to the PCM. The PCM doesn't like it and lights up the check engine light (CEL).
2. 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.
3. 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.
4. 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.

More 3.0L Ford Escape Tutorials

You can find more 3.0L Ford Escape (Mazda Tribute) tutorials in these indexes:

• Ford 3.0L Index Of Articles.
• Ford 3.0L Index Of Articles (at: troubleshootmyvehicle.com).

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

• How To Test The Cooling Fan Motors (2001-2004 Ford Escape - Mazda Tribute).
• How To Test The Throttle Position Sensor (2001-2007 3.0L Ford Escape).
• How To Test The Ford Escape COP Coils (Troubleshooting A Misfire).