How To Test The Throttle Position Sensor (1997-2000 4.2L V6 Ford E150, E250)

The throttle position sensor (TPS) is probably one of the easiest components to test on the 4.2L V6 Ford E150 or E250 van.

In this tutorial, I'll show you how to test it with a multimeter. With your test results, you'll be able to quickly find out if it's working correctly or if it's bad and needs to be replaced.

APPLIES TO: This tutorial applies to the following vehicles:

• 4.2L V6 Ford E150: 1997, 1998, 1999, 2000.
• 4.2L V6 Ford E250: 1997, 1998, 1999, 2000.

F-SERIES PICKUPS: The TP sensor test tutorial for the 1997-2000 4.2L V6 Ford F150/F250 can be found here:

• How To Test The Throttle Position Sensor (1997-2000 4.2L V6 Ford F150, F250) (at: easyautodiagnostics.com).

Symptoms Of A Bad Throttle Position Sensor

The throttle position sensor (TPS) is the component that tells the fuel injection computer how the throttle plate opens/closes as you're stepping on or off the accelerator pedal.

This throttle plate angle information is then sent to the fuel injection computer so that it can do it's little song and dance and keep the engine running optimally.

As you're probably already aware, when the throttle plate opens, more air enters the engine. As you let off the gas pedal the throttle plate closes and less air enters the engine. This makes the throttle position sensor a critical engine management component. So when it fails, you're going to see one or more of the following problems:

• Check Engine Light: The check engine light will be triggered by one of the following diagnostic trouble codes (DTCs):
  • P0122: Throttle Position Sensor Circuit Low Input.
  • P0123: Throttle Position Sensor Circuit High Input.
• Engine Performance Issues: You'll see one or more of the following:
  • Engine hesitates when you step on the accelerator pedal.
  • Lack of power when accelerating the vehicle.
  • Engine idle either too high or too low.
  • Rough engine idle.
  • The engine may start and immediately stall.
• Bad Gas Mileage: The fuel injection computer will run an excessively rich air/fuel mixture which will hurt gas mileage.
• Engine No-Start: The engine cranks but does not start.

Throttle Position Sensor (TPS) Circuit Descriptions

I'm sure you've already noticed that the throttle position sensor has three wires coming out of its pigtail connector.

Each wire has a specific role, and the table below gives a brief description of each:

Terminal	Wire	Description
1	Brown with white stripe (BRN/WHT)	5 Volts (from PCM)
2	Gray with white stripe (GRY/WHT)	TPS Signal
3	Gray with red stripe (GRY/RED)	Ground (from PCM)

Where To Buy The TPS And Save

The following links will help you comparison shop for the throttle position sensor (of known professional automotive brands- NO knock-offs):

TEST 1: TPS Voltage Signal Check Key On Engine Off

To get our TPS sensor diagnostic started, we're going to check the performance of the TPS.

This first test, we're going to do by connecting our multimeter to the TPS signal wire. With the key on engine off, we should have around 0.4 to 0.7 Volts DC.

The wire that we're going to connect our multimeter to, is the grey with white stripe (GRY/WHT) wire that I've labeled with the number 2.

Will do a simple multimeter test to confirm the 0.4 to 0.7 Volts DC in the TPS signal wire.

IMPORTANT: The throttle position sensor must remain connected to its connector in order to access the signal in the wire. You'll need to use a back-probe on the connector or a wire-piercing probe on the wire. You can see what this tool looks like and where to buy it here: Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link).

Let's get started:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Connect the red multimeter test lead to the grey with white stripe (GRY/WHT) wire of the TP sensor harness connector.
   
   I've labeled the GRY/WHT wire with the number 2 in the photo above.
   
   NOTE: The TPS must remain connected to its connector to test the TPS voltage signal.

3. 3

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

4. 4

   Turn the key on but don't crank or start the engine.

5. 5

   Your multimeter should register 0.4 to 0.7 Volts DC.

Let's analyze your test results:

CASE 1: The multimeter registered between 0.4 to 0.7 Volts DC. This is the correct test result.

Your next step is to go to: TEST 2: Testing The TPS Voltage Signal.

CASE 1: The multimeter DID NOT register between 0.4 to 0.7 Volts DC. This tells you that something is definitely wrong with the TPS sensor.

Your next step is to go to: TEST 2: Testing The TPS Voltage Signal.

TEST 2: Testing The TPS Voltage Signal

For our second test, we're gonna check the TPS signal output by manually opening and closing the throttle plate.

The test result that'll tell us the TPS is OK, is a TPS signal voltage that increases as we open the throttle plate and decreases as we close the throttle plate.

As in TEST 1, we're going to check this TPS voltage output on the GRY/WHT wire that I've labeled with the number 2.

IMPORTANT: The throttle position sensor must remain connected to its connector in order to access the signal in the wire. You'll need to use a back-probe on the connector or a wire-piercing probe on the wire. You can see what this tool looks like and where to buy it here: Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link).

Let's get started:

1. 1

   Place your multimeter in Volts DC mode.

2. 2

   Connect the red multimeter test lead to the grey with white stripe (GRY/WHT) wire of the TP sensor harness connector.
   
   I've labeled the GRY/WHT wire with the number 2 in the photo above.
   
   NOTE: The TPS must remain connected to its connector to test the TPS voltage signal.

3. 3

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

4. 4

   Turn the key on but don't crank or start the engine.

5. 5

   Manually rotate the throttle plate to its open position.
   
   You'll get the best results by opening and closing the throttle plate directly on the throttle body instead of stepping on the accelerator pedal.

6. 6

   The multimeter should show an increasing voltage as you (or your helper) open up the throttle plate.

7. 7

   Close the throttle plate as you observer the multimeter.

8. 8

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

9. 9

   Using a screwdriver's handle, gently tap the TP sensor as you open and close the throttle plate and observe the multimeter.
   
   The purpose (of tapping the TP sensor with the screwdriver's handle) is to see if the TP sensor shows gaps 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 analyze your test results:

CASE 1: The TPS voltage signal increased/decreased as you opened/closed the throttle plate. This is the correct test result and it indicates that the throttle position sensor is good.

With this test result you can also conclude that the TPS sensor is getting both power (5 Volts) and Ground from the fuel injection computer.

CASE 2: The TPS voltage signal DID NOT increase/decrease as you opened and closed the throttle plate. This test result usually indicates that the TPS sensor is defective.

To make sure the TPS sensor is bad the next step is to check that the BRN/WHT wire is feeding the TPS with 5 Volts. For this test go to: TEST 3: Making Sure The TPS Is Receiving 5 Volts.

CASE 3: The multimeter DID NOT register any voltage. This test result usually indicates that the TPS sensor is defective.

To make sure the TPS sensor is bad the next step is to check that the BRN/WHT wire is feeding the TPS with 5 Volts. For this test go to: TEST 3: Making Sure The TPS Is Receiving 5 Volts.

TEST 3: Making Sure The TPS Is Receiving 5 Volts

In this test section, we're going to check that the throttle position sensor is getting power, which is in the form of 5 Volts DC and are provided by the fuel injection computer.

The wire that delivers these 5 Volts is the one that I've labeled with the number 1 in the photo above. This is the brown with white stripe (BRN/WHT) wire of the TPS 3-wire connector.

If the TPS is receiving power, your multimeter should register a voltage between 4.5 to 5 Volts DC.

Let's get testing:

1. 1

   Disconnect the TPS from its electrical connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

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

4. 4

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

5. 5

   With the red multimeter test lead, gently probe the female terminal that connects to the brown with white stripe (BRN/WHT) wire of the TPS connector.
   
   I've labeled the BRN/WHT wire with the number 1 in the photo above.

6. 6

   Your multimeter should read 4.5 to 5 Volts DC.

Let's analyze your test results:

CASE 1: The BRN/WHT wire is feeding the TPS with 5 Volts. This is the correct test result.

Now that you have confirmed the TPS is getting 5 Volts, the next step is to make sure it's getting Ground. Go to: TEST 4: Making Sure That The TPS Is Receiving Ground.

CASE 2: The BRN/WHT wire IS NOT feeding the TPS with 5 Volts. Without these 5 Volts the TPS will not function.

These missing 5 Volts are usually the result of an open-circuit problem in the BRN/WHT wire between the TPS sensor's connector and the fuel injection computer's connector.

TEST 4: Making Sure That The TPS Is Receiving Ground

Up to this point you have:

• Checked the TPS voltage output with the key on engine off (TEST 1).
• Confirmed that the TPS signal does not increase/decrease as you open/close the throttle plate (TEST 2).
• Confirmed that the TPS is getting 5 Volts (TEST 3).

In this last test section, we're going to check that the TPS is getting Ground. As with the 5 Volts, this Ground is provided by the fuel injection computer.

The wire that delivers Ground to the TPS is the one I've labeled with the number 3 in the photo above and it'll be the grey with red stripe (GRY/RED) wire of the 3-wire connector.

IMPORTANT: Be careful not to short the Ground wire to battery power, or you'll fry the fuel injection computer. The multimeter voltage test suggested below (to test the Ground circuit) is a safe and accurate test.

These are the test steps:

1. 1

   Disconnect the TPS from its electrical connector.

2. 2

   Place your multimeter in Volts DC mode.

3. 3

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

4. 4

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

5. 5

   With the black multimeter test lead, gently probe the female terminal that connects to the grey with red stripe (GRY/RED) wire of the TPS connector.
   
   I've labeled the GRY/RED wire with the number 3 in the photo above.

6. 6

   Your multimeter should read 10 to 12 Volts DC.

Let's analyze your test results:

CASE 1: The GRY/RED wire is feeding Ground to the TPS. This is the correct test result.

You can correctly conclude that the TPS is defective if you have:

• Checked the TPS voltage output with the key on engine off (TEST 1).
• Confirmed that the TPS voltage signal does not increase/decrease as you opened/closed the throttle plate (TEST 2).
• Confirmed that the TPS is getting 5 Volts (TEST 3).
• Confirmed, in this test section, that the TPS is getting Ground.

CASE 2: The GRY/RED wire IS NOT feeding Ground to the TPS. Without Ground the TPS will not function.

This missing Ground is usually caused by an open-circuit problem in the GRY/RED wire between the throttle position sensor's connector and the fuel injection computer's connector.

More 4.2L Ford E150 And E250 Test Tutorials

If this tutorial was helpful, be sure and take a look at all of the 4.2L V6 E150 and E250 diagnostic tutorials in this index:

• 4.2L Ford E150 And E250 Index of Articles.

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

• How To Test Engine Compression (1997-2003 4.2L V6 Ford E150, E250).
• How To Test The Fuel Pump (1997-2000 4.2L V6 Ford E150, E250).
• How To Test The CKP Sensor With A Multimeter (1997-2003 4.2L V6 Ford E150, E250).
• How To Test For A Blown Head Gasket (1997-2003 4.2L V6 Ford E150, E250).