How To Test: Throttle Position Sensor (Ford 1.9L, 2.0L)

The throttle position sensor (TPS) is one of the easiest sensors to test on your Ford 1.9L or 2.0L 4 cylinder engine.

The best part of testing the TPS is that you don't need any expensive tools. You can test it with a simple multimeter. Yep, no scan tool is required for the TPS test.

Also you don't need to remove the TPS from its place on the throttle body to test it since it can be tested while it's still on the engine.

In this tutorial I'm gonna explain the whole test in a step by step manner.

Symptoms Of A Bad Throttle Position Sensor (TPS)

Your vehicle's computer needs to know how much the throttle plate opens, when you step on the accelerator pedal, so that it can inject more fuel.

It also needs to know when the throttle plate closes, as you're letting your foot off of the accelerator pedal, so that it can inject less fuel.

So, when the TP sensor fails, the fuel injection computer isn't able to effectively control the amount of fuel injection (and a host of other things) and you're gonna' feel it as you drive your vehicle down the road.

Here an other symptoms of a bad throttle position sensor (TPS) your Ford vehicle may experience:

1. Trouble codes lighting up the check engine light (CEL):
   • Code P0120: Throttle Position (TP) Circuit Performance Problem.
   • Code P0123: Throttle Position (TP) Circuit High Input.
   • Code P0122: Throttle Position (TP) Circuit Low Input.
2. Hesitation when accelerating your vehicle down the road.
3. Intermittent lack of power when accelerating.
4. Bad gas mileage.
5. Extended cranking time.
6. Idle lopes (idle RPMs go up and down).

Basics Of The Throttle Position Sensor (TPS)

The throttle position sensor (TPS) is located on the side of the throttle body.

As you're already aware, the throttle position sensor (TPS) on your 1.9L or 2.0L equipped Ford has 3 wires coming out of its connector.

Each wire starts and ends at the fuel injection computer (known in today's tech lingo as the Powertrain Control Module = PCM).

Each one carries a specific type of signal and in this section, I'll briefly go over each one.

NOTE: You'll notice in the descriptions below that I did not include the color of the wires. This shouldn't worry you because the circuits are the same regardless of the color of the wires on your specific Ford model. (as long as they're covered by this tutorial -see the ‘Applies To:’ box on the right).

TPS circuit descriptions:

• Circuit labeled 1:
  • Ground (provided by the PCM).
• Circuit labeled 2:
  • Throttle Position (TP) Signal Circuit.
  • The TP signal's voltage increases as the throttle angle increases.
  • The TP signal's voltage decreases as the throttle angle decreases.
• Circuit labeled 3:
  • Power in the for of 5 Volts DC (provided by the PCM).

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

The very first TPS test that we're going to do is to test its ability to produce a throttle angle position signal.

This involves connecting your multimeter (which will be set to Volts DC mode) to the wire labeled with the number 2.

And then manually opening the throttle plate to see if the sensor produces an increasing voltage as you open the plate and a decreasing voltage as you close the throttle plate back to its normally closed position.

If the signal doesn't move (increase or decrease) or the voltage signal shows gaps, then the TP sensor is bad and needs to be replaced.

If you don't have a multimeter or need to upgrade yours? Check out my recommendation: Tekpower TP8268 AC/DC Auto/Manual Range Digital Multimeter (Amazon affiliate link).

IMPORTANT: Remember this is an on car test of the sensor, even though the images of the TPS show it off of the engine. The images show the TPS off of the engine just to make it easier to explain the multimeter connection you need to make.

Here are the test steps:

1. 1

   Turn the key to the ON position but don't crank or start the engine.

2. 2

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

3. 3

   Place your multimeter in Volts DC mode and connect the red test lead to the wire that connects to female terminal 2 of the TPS connector. This is the middle wire of the connector.
   
   NOTE: The TP sensor connector needs to remain connected to the TPS during this test, 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: Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link)).

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.

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 the first of these two, go to: TEST 2: Making Sure The TPS Is Getting Power.

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.

TEST 2: Making Sure The TPS Is Getting Power

If the TPS doesn't get power or Ground, it's not going to function. So in this test section, we're going to check to see if the TPS is getting power with our multimeter (we'll check for Ground in TEST 3).

This power comes in the form of 5 Volts DC and is provided by your vehicle's fuel injection computer.

The terminal of the TPS connector that delivers this voltage to the sensor is the one I've labeled with the number 3 in the illustration above.

If your test results confirm that the TPS is getting power, we'll move on to TEST 3 and make sure the fuel injection computer is also providing Ground.

Let's get going:

1. 1

   Disconnect the TP sensor from its 3-wire connector.

2. 2

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

3. 3

   Put your multimeter in Volts DC mode.

4. 4

   Turn the key to its ON position but do not start the engine.

5. 5

   Gently probe the female terminal labeled with the number 3 with the red multimeter test lead (see illustration above).

6. 6

   Your multimeter should read 4.5 to 5 Volts.

Let's take a look at your test results:

CASE 1: Power (5 Volts) is present. This is the correct and expected test result.

Now that you've confirmed that the TPS sensor is getting 5 Volts from the fuel injection computer, our next and final step is to make sure that it's getting Ground. Head over to: TEST 3: Making Sure The TPS Is Getting Ground.

CASE 2: Power IS NOT present. Double-check your test connections and repeat the test.

If you still don't see 4.5 to 5 Volts present at female terminal 3, then we can rule out the TPS sensor as defective, since without power, it's not going to function.

Although this is beyond the scope of this tutorial, your next step is to find out why these 5 Volts are missing and restore them to the circuit.

The most likely cause of this missing 5 Volts is an open-circuit problem in the wire between the TPS connector and the PCM connector.

TEST 3: Making Sure The TPS Is Getting Ground

Up to this point, your diagnostic tests have confirmed the following:

• TPS signal —the voltage signal is either stuck or missing regardless of throttle plate position.
• Power present —the TPS is getting 5 Volts from the PCM.

For our final diagnostic test, we need to make sure that the TPS is getting Ground. This is a PCM-supplied Ground and is only available with the key in the ON or RUN position.

For our testing purposes, we'll check it with the key in the ON position but with the engine OFF.

NOTE: Be very careful when testing this circuit. Do not connect this circuit to battery voltage, or you'll damage the PCM. The multimeter voltage test outlined below is a safe way to check for the presence of this Ground in the circuit.

OK, let's get to it:

1. 1

   Disconnect the TP sensor from its 3-wire connector.

2. 2

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

3. 3

   Put your multimeter in Volts DC mode.

4. 4

   Turn the key to its ON position but do not start the engine.

5. 5

   Gently probe the female terminal labeled with the number 1 with the black multimeter test lead (see illustration above).

6. 6

   Your multimeter should read 10 to 12 Volts.

Alright, let's find out what it all means:

CASE 1: Ground is present. This is the correct and expected test result and confirms that the fuel injection computer in your Ford vehicle is delivering the Ground the TP sensor needs to function.

You can conclude that the TP sensor is bad and needs to be replaced if you have confirmed the following conditions to be true:

• No TP signal —The signal is stuck or missing no matter how much you open or close the throttle plate (TEST 1).
• Power present —The TP sensor is getting 5 Volts from the fuel injection computer (TEST 2).
• Ground present —In this final test section, you've confirmed that it is getting Ground.

CASE 2: Ground IS NOT present. Double-check your test connections and repeat the test.

If your multimeter doesn't register a voltage of 10 to 12 Volts at female terminal 1, then we can rule out the TPS sensor as defective, since without Ground, it's not going to function.

Although this is beyond the scope of this tutorial, your next step is to find out why this PCM-supplied Ground is missing and restore it to the circuit.

The most likely cause of this missing Ground is an open-circuit problem in the wire between the TPS connector and the PCM connector.

Throttle Position Sensor (TPS) Is Good But Code Won't Go Away

If you're reading this section then you have probably already replaced the TPS and it didn't solve the problem and or the check engine light won't go away (the TPS trouble code that is). You may have also tested the TPS and the results indicate that the TPS is good and you're wondering what to do next.

If this is your predicament, in this section I have a few tips that may be of help. The most important thing you've done has been eliminating the TP sensor as the source of the problem (trouble code) itself. Your next steps should be:

1. Checking the adjustment of the throttle plate stop set screw.
   • This screw's adjustment usually has been altered to idle up the engine and mask a rough idle condition. The PCM doesn't like it when this is done and sets a TP sensor code.
2. Check the continuity of the TP sensor's wires (between the PCM and the TP sensor connector).
   • If there's a break in any of the 3 wires, the PCM will set a TP sensor code.
3. Check for a bad fuel injection computer (PCM).
   • Is there a way to test for a bad PCM? Yes and no. The only way to test for a bad PCM is to test it indirectly. This is what I do to test for a bad PCM (with about a 98% success rate):
     • Eliminate the TP sensor itself as bad.
     • Check the continuity of the 3 TP sensor wires (between the PCM and the sensor). The idea here is to make that none of the TP sensor wires are cut (‘open’).
     • Check all of the PCM Ground wires by doing a voltage drop test on them. This simply involves checking the Ground wire for voltage (not Ohms) with the Key On Engine Off. There should be no voltage on the wire. If there's voltage (2 Volts or more) that specific Ground wire is not providing a good path to Ground and it means you need to clean the Ground terminals and/or check their condition.
     • Check that the PCM is getting power on the all of it's power circuits.
     • After eliminating the TP sensor, a problem in the 3 TP sensor wires (between the PCM and sensor), eliminating the PCM's Ground wires, and verifying the PCM is getting power on all its power circuits, then, and only then I can say with confidence that the PCM is bad.

The key to testing all of the above (and either exonerating or blaming the PCM as bad) requires that you have the specific wiring diagram for your particular Ford vehicle.

More ‘How To Test’ Tutorials

You can find a pretty big list of Ford tutorials in this index: Ford 1.9L, 2.0L Index Of Articles.

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

• How To Test The Ford EGR Valve EGR Vacuum Solenoid, DPFE Sensor (at: easyautodiagnostics.com).
• MAF Sensor TEST 2.0L Escort, Tracer (1997-2002) (at: easyautodiagnostics.com).
• How To Test The Coil Pack (Ford 1.9L, 2.0L) (at: easyautodiagnostics.com).
• How To Test The Alternator (Ford 1.9L, 2.0L).
• How To Test The Starter Motor (Ford 1.9L, 2.0L).