How To Test The TPS With A Multimeter (1996-2007 3.0L V6 Ford Taurus, Mercury Sable)

The throttle position sensor (TPS) on the 1996-2007 3.0L V6 Ford Taurus or Mercury Sable can be tested with a multimeter.

Yep —you don't need any expensive diagnostic equipment to see if the sensor's toast and needs to be replaced, or if the issue is something else.

In this tutorial, I'm going to show you how easy it is to see if it's producing the correct TPS signal voltage and to check if it's getting VREF (5 Volts) power and SIG RTN Ground from the powertrain control module (PCM).

All these tests are super easy to do, and they're all explained step by step in this tutorial.

APPLIES TO: This tutorial applies to the following vehicles:

• 3.0L V6 Ford Taurus: 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007.
• 3.0L V6 Mercury Sable: 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007.

1991-1995 TPS DIAGNOSTIC TESTS:

• How To Test The TPS With A Multimeter (1991-1995 3.0L V6 Ford Taurus, Mercury Sable).

Symptoms Of A Bad TPS

In a nutshell, the TPS tells the PCM how much the throttle opens or closes as you step on or off the gas pedal, since they're both connected by an accelerator cable.

Because the info the TPS gives the PCM is critical for keeping the engine running smoothly, when the sensor fails, all kinds of havoc break out. You'll run into one or more of the following engine performance issues.

• You're going to see one of the following TPS diagnostic trouble codes (DTCs):
  • P0121: Throttle Position (TP) Circuit Performance Problem.
  • P0122: Throttle Position (TP) Circuit Low Input.
  • P0123: Throttle Position (TP) Circuit High Input.
• Bad gas mileage.
• Erratic shifting from the automatic transmission.
• Lack of power as you exit the vehicle on the road.
• The motor jerks when you step on the accelerator when you're driving down the road.

Where To Buy The TPS And Save

Online, you'll find plenty of knock-off brands when it comes to buying the throttle position sensor for your Taurus or Sable. I want to recommend the following two well-known automotive brands I've used for years that won't break the bank.

I don't hesitate to recommend them because of their quality and durability. You don't want that brand-new sensor failing on you in just a few weeks.

Circuit Descriptions Of The TPS

As you probably already know, the TPS has three wires coming out of its connector. To successfully diagnose and test the sensor, we need to know what each wire (circuit) does.

The following table gives a brief description of each circuit to help us in the tests that follow.

• Terminal #1:
  • VREF —5 Volts (from FI computer).
• Terminal #2:
  • TPS —Throttle position angle signal.
• Terminal #3:
  • SIG RTN —Sensor Ground (from FI computer).

TEST 1: Testing The Throttle Position Signal With A Multimeter

As I mentioned earlier, the TP sensor's job is to inform the PCM of the throttle plate's angle. The cool thing is you and I can easily confirm if the sensor's doing what it should.

What I mean is, we can tap into the sensor's TP signal wire with a multimeter, then manually open and close the throttle plate to see if it's producing the correct throttle angle signal.

The wire we'll be tapping into is the gray with white stripe (GRY/WHT) wire of the TP sensor's 3-wire connector.

Now, keep in mind that to test the TP signal with a multimeter, the sensor has to stay connected to its 3-wire connector. You'll need to either back probe the connector or use a wire-piercing probe on the wire itself to read the signal. If you don't have either of these tools, here's the one I use and recommend:

• Goupchn 4mm Banana to Banana Plug Test Leads Kit (Amazon affiliate link).

Here are the test steps:

1. 1

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

2. 2

   Set your multimeter to DC Volts mode.

3. 3

   Turn the key to the ON position (engine OFF). Don't crank or start the engine.
   
   This step powers up the TPS.

4. 4

   Probe the middle wire of the TPS connector with the red multimeter test lead and an appropriate tool (like a back probe or a wire-piercing probe).
   
   The middle wire of the TPS connector should be a gray with white stripe (GRY/WHT) wire.
   
   NOTE: The TPS must stay connected to its 3-wire connector during this test.

5. 5

   With the throttle plate completely closed, the voltage should read between 0.3 and 0.9 Volts DC.
   
   This is your base reading.

6. 6

   Open the throttle plate slowly by hand. The voltage should climb smoothly as the plate opens.

7. 7

   At wide open throttle (WOT), the voltage should be between 3.5 and 4.5 Volts DC.

8. 8

   Close the throttle plate slowly. The voltage should fall back down to the same number you recorded in step 5.
   
   Verify that the closed-throttle reading matches your starting value.

9. 9

   Lightly tap the TPS body with the handle of a screwdriver while opening and closing the throttle plate.
   
   NOTE: Tapping on the sensor should not cause the readings to spike, cut out, or glitch. If it does, the TPS is faulty and must be replaced.

Let's take a look at your test results:

CASE 1: The TP signal voltage increased/decreased as you opened/closed the throttle plate. Good —this is the correct and expected test result, and it tells you the throttle position sensor is working properly.

If you have a TPS trouble code P0122 (TPS Circuit Low) or P0123 (TPS Circuit High), then whatever triggered them isn't happening right now since the TPS signal isn't stuck low or high and is correctly reporting throttle plate angle.

CASE 2: The TP sensor voltage did not increase/decrease as you opened/closed the throttle plate. This usually means the sensor is toast and needs to be replaced.

But to be sure, we need to confirm that the sensor is getting VREF power and SIG RTN Ground. For the first of these two tests, go to: TEST 2: Making Sure The TPS Is Getting VREF Power.

CASE 3: Your multimeter did not report any TP signal voltage (0 Volts). This usually means the sensor isn't getting VREF power or SIG RTN Ground.

For your next step, make sure the TP sensor is getting VREF power, and then confirm it's getting SIG RTN Ground. For the first of these two tests, go to: TEST 2: Making Sure The TPS Is Getting VREF Power.

TEST 2: Making Sure The TPS Is Getting VREF Power

Alright, if you're starting this test section, then TEST 1 has confirmed the TP sensor isn't doing what it should. In other words, its output signal voltage is stuck no matter how much you move the throttle plate.

For our next test, we're going to make sure the PCM is supplying the TP sensor with 5 Volts VREF power through the brown with white stripe (BRN/WHT) wire.

The BRN/WHT wire connects to female terminal 3 of the sensor's 3-wire connector.

Since these 5 Volts come from your Taurus or Sable's PCM, they're only available when the key is in the RUN or START position. For our testing purposes, we'll be checking with the key in RUN but the engine OFF.

NOTE: Be careful when probing the front of the female terminals on the connector with your multimeter test leads. You want to avoid damaging the connector and permanently spreading the terminal. If that happens, you'll need to replace the connector with a new one.

Here are the test steps:

1. 1

   Disconnect the TPS from its 3-wire connector.

2. 2

   Switch the key to the RUN position (ON) but don't crank or start the engine.

3. 3

   Set your multimeter to Volts DC mode.

4. 4

   Connect the black multimeter test lead to the battery's negative (-) post.

5. 5

   Gently probe the front of female terminal 1 with the red multimeter lead
   
   NOTE: Check that terminal 1 connects to the BRN/WHT wire of the connector.

6. 6

   The multimeter should show between 4.5 and 5.0 Volts DC.

Let's take a look at your test results:

CASE 1: Terminal 1 has 4.5 to 5 Volts. This confirms the TP sensor is getting VREF voltage from the PCM.

Now that you've confirmed the BRN/WHT wire is delivering VREF voltage to the sensor, your next diagnostic step is to make sure the sensor is also receiving SIG RTN Ground from the PCM. Head over to: TEST 3: Making Sure The TPS Is Getting SIG RTN Ground.

CASE 2: Terminal 1 doesn't have 5 Volts present. This test result tells you the sensor itself is OK, since without these 5 Volts, it won't function.

Although it's beyond the scope of this tutorial to troubleshoot this missing VREF voltage, your next step is to track down the cause and restore it to the circuit. Once the sensor gets 5 Volts, it'll work again.

TEST 3: Making Sure The TPS Is Getting SIG RTN Ground

Your previous two tests have confirmed the following:

• The TP signal is stuck at one value no matter how much you open or close the throttle plate (TEST 1).
• The BRN/WHT wire is delivering 5V VREF power to the sensor (TEST 2).

The last thing we're going to check is that the PCM is supplying the sensor with SIG RTN Ground.

This SIG RTN Ground is delivered to terminal 3 of the TP sensor's connector by the gray with red stripe (GRY/RED) wire.

Since this Ground comes directly from the PCM, it's only available with the key in the RUN or START position. For our test, we'll check it with the key in RUN but the engine OFF.

IMPORTANT: Be careful when testing this circuit, since this Ground is supplied by the PCM. Don't accidentally —or intentionally— apply 12V directly from the battery to this terminal or wire. Doing so will deep fry the PCM. The multimeter voltage test we're about to do below is a safe way to check for the presence of SIG RTN Ground in this circuit.

Here are the test steps:

1. 1

   Disconnect the TPS from its 3-wire connector.

2. 2

   Switch the key to the RUN position (ON) but don't crank or start the engine.

3. 3

   Set your multimeter to Volts DC mode.

4. 4

   Connect the red multimeter test lead to the battery's positive (+) post.

5. 5

   Gently probe the front of female terminal 3 with the black multimeter lead
   
   NOTE: Check that terminal 3 connects to the GRY/RED wire of the connector.

6. 6

   The multimeter should show between 10 to 12 Volts DC if the SIG RTN Ground is present at terminal 3.

Let's what your SIG RTN Ground test result means:

CASE 1: Terminal 3 is supplying SIG RTN Ground. This is the correct and expected test result, and it tells you the TP sensor is getting the Ground it needs to function from the PCM.

If you've checked and confirmed the following, then you can conclude the sensor is fried and needs to be replaced:

• In TEST 1, the TP signal is stuck at one value no matter how much you move the throttle plate.
• In TEST 2, you confirmed the sensor is getting 5 Volts VREF from the PCM.
• In this test, you confirmed the PCM is supplying SIG RTN Ground to the sensor.

Whenever you're ready to replace the TP sensor, I recommend the following sensors from Walker Products and Delphi, brands I've used for years and don't hesitate to recommend:

• Walker Products 200-1064 Throttle Position Sensor (Amazon affiliate link).
• Delphi SS11437 Throttle Position Sensor (Amazon affiliate link).

CASE 2: Terminal 3 is not supplying SIG RTN Ground. Without this Ground, the TP sensor won't function. With this test result, we can also rule out the sensor itself as the cause of the engine performance issue and TPS trouble code.

Your next step is to find out why this SIG RTN Ground is missing and restore it to the circuit. Once the TP sensor starts receiving this PCM-supplied Ground, it'll work again.

The most likely cause of the missing SIG RTN Ground is an open-circuit problem in the wire between the TP sensor connector and the PCM.

More 3.0L V6 Ford Taurus Diagnostic Tutorials

You can find a complete list of diagnostics tutorials for the 3.0L V6 Taurus and Mercury Sable in this index:

• 3.0L V6 Ford Taurus Index Of Articles.

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

• How To Test The MAF Sensor (1991-1995 3.0L V6 Ford Taurus, Mercury Sable).
• How To Test For A Blown Head Gasket (1990-2007 3.0L V6 Ford Taurus, Mercury Sable).
• How To Test The Fuel Injectors (1991-1995 3.0L Ford Taurus).
• How To Do And Interpret An Engine Compression Test (1990-2007 3.0L V6 Ford Taurus, Mercury Sable).