How To Test The TPS -1994-1995 3.0L Ford Taurus

The throttle position sensor on the 1991 through 1995 Ford Taurus or 3.0L V6 Mercury Sable can be easily checked with a multimeter.

You don't need a scan tool to find out if it's good or bad. Initiatory I'm going to show you how to do the test step by step so that you can find out if it's defective or not.

You can find this tutorial in Spanish here: Cómo Probar El Sensor TPS (1994-1995 3.0L Taurus) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 3.0L V6 Ford Taurus: 1991, 1992, 1993, 1994, 1995.
• 3.0L V6 Mercury Sable: 1991, 1992, 1993, 1994, 1995.

Symptoms Of A Bad TPS

As you're probably already aware, fuel injection (FI) computer is constantly monitoring all of the input centers of the fuel injection system, to see if they are functioning within normal parameters. So, when the throttle position sensor fails, the fuel injection computer is going to light up the check engine light with a trouble code:

1. You're going to see one of the following trouble codes
   • 121: TPS Voltage Higher Or Lower Than Expected.
   • 122: TPS Circuit Below Minimum Voltage.
   • 123: TPS Circuit Above Maximum Voltage.
   • 124: TPS Voltage Higher Than Expected.
   • 125: TPS Voltage Lower Than Expected.
2. Bad gas mileage.
3. Erratic shifting from the automatic transmission.
4. Lack of power as you exit the vehicle on the road.
5. The motor jerks when you step on the accelerator when you're driving down the road.

Where To Buy The TPS And Save

The following links will help you too compare prices on the throttle position sensor NH electrical connector:

Circuit Descriptions Of The TPS

The throttle position sensor electrical connector, on the 1991 through 1995 3.0L V6 Ford Taurus (Mercury Sable), has 3 wires coming out of it. Each one is responsible to feed or transmit 5 Volts, brown, or the throttle position angle signal to the FI computer.

Below you're going to find a brief description what each cable does:

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

IMPORTANT: Each of these three wires connect directly to the fuel injection computer. For this reason you need to be very careful not to intentionally or accidentally short-circuit the SIG RTN Ground wire to 12 Volts (or you're gonna fry the fuel injection computer).

NOTE: The throttle position sensor itself has male spade terminals while its connector has female type terminals.

TEST 1: Testing The Throttle Position Signal With A Multimeter

When the throttle plate in the throttle body is closed on the 1991-1995 3.0L V6 Ford Taurus (3.0L Mercury Sable), the throttle position sensor produces a voltage of about 0.5 Volts DC.

This voltage increases as the throttle plate opens. When the throttle plate opens too it's completely open position, the sensor generates a voltage of about 4.5 Volts DC.

So, in this section, we're going to connect a multimeter to the throttle position sensors metal wire to see if it's generating the correct signal as we open and close the throttle plate.

NOTE: The TPS has to remain connected to its electrical connector to be able to read the throttle position signal. For this reason, you're gonna need a back-probe tool or a wire piercing probe. If you don't have one, this is 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 sensor signal's voltage increased or decreased smoothly and without gaps. This is the correct and expected test result and lets you know that the throttle position sensor, on your 1991-1995 3.0L V6 Ford Taurus, is OK. This test result also tells you that the TPS is getting Ground and Power.

CASE 2: The TP sensor signal's voltage DID NOT increase or decrease smoothly and/or showed gaps. This test result usually tells you that the throttle position sensor (TPS) is fried and needs to be replaced but not always.

We need to do two more tests to make sure and the first of these two is to make sure its getting VREF 5 Volts. For this test, go to: TEST 2: Making Sure The TPS Is Getting VREF Power.

TEST 2: Making Sure The TPS Is Getting VREF Power

If you've reached this point, then the throttle position sensor on your 3.0L V6 Ford Taurus (Mercury Sable) failed TEST 1.

So, in this section, we're going to make sure that the TPS is getting 5 Volts. This VREF voltage is delivered to female terminal 1 (of the connector) by the brown with white stripe (BRN/WHT) wire.

Since your Taurus or Sable's fuel injection (FI) computer is the one that provides this VREF voltage, we need to make sure it's present at terminal 1 with the key in the RUN position but with the engine OFF.

NOTE: Be careful when probing the front of the female terminal. The multimeter test lead could damage the terminal if you press too hard with it. Be careful and don't damage the terminal or the connector, otherwise you'll have to replace the connector.

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: 5 Volts are present at terminal 1. This is the correct and expected test result.

Now that we've confirmed that the FI computer is providing VREF voltage, our next test is to make sure that it's also supplying the sensor with SIG RTN Ground. For this test, go to: TEST 3: Making Sure The TPS Is Getting SIG RTN Ground.

CASE 2: 5 Volts ARE NOT present at terminal 1. This test result exonerates the TP sensor as being bad and tells you that the reason the TP sensor is not producing an increasing/decreasing voltage signal in TEST 1 is because it's missing VREF power.

Although it's beyond the scope of this tutorial, you'll need to find out why these 5 Volts are missing (and restore them to the circuit) to get the TP sensor back on the job.

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

All right, up to this point, your TPS diagnostic has revealed the following:

• The TPS signal is stuck, no matter how much you open or close the throttle (TEST 1).
• The brown-white wire is supplying SIG VREF 5 Volts power at terminal 1 (TEST 2).

For our final diagnostic test, we're going to make sure that the FI computer is supplying the SIG RTN Ground to the sensor via the gray with red stripe (GRY/RED) wire —which connects to terminal 3 of the sensor's 3-wire connector.

This SIG RTN Ground is only available with a key in the RUN or START position. For our test, we're going to check it with a key in the RUN position, but with the engine OFF.

IMPORTANT: Be careful not to connect 12 Volts (from the battery) to this circuit (wire), or you're going to deep-fry the FI computer. The multimeter voltage test I'm outlining in the test steps that follow is a safe way to check for the presence of SIG RTN Ground at terminal 3.

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 take a look at your test results:

CASE 1: SIG RTN Ground is present at terminal 3. This is the correct and expected test result.

If you have confirmed the following, then you can conclude that the throttle position sensor on your Taurus or Sable is toast and needs to be replaced:

• The TP signal doesn't change when you open/close the throttle (TEST 1).
• The BRN/WHT wire is delivering 5V VREF power (TEST 2).
• In this test section, you've confirmed that the GRY/RED wire is delivering SIG RTN Ground.

CASE 2: SIG RTN Ground IS NOT present at terminal 3. This test result exonerates the TP sensor as being bad and tells you that the reason the TP sensor is not producing an increasing/decreasing voltage signal in TEST 1 is because it's missing this computer-supplied Ground.

Although it's beyond the scope of this tutorial, you'll need to find out why the SIG RTN Ground is missing and restore it to the circuit to get the TP sensor back on the job.

TPS Trouble Code Won't Go Away

In certain cases, the fuel injection computer continues to set a throttle position sensor diagnostic trouble code even though the sensor is brand new (or you've already checked it's working correctly with a multimeter).

If this is what's happening in your particular case, then the following suggestions should help you to resolve the problem:

1. Check 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 FI computer 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 FI computer and the TP sensor connector).

   If there's a break in any of the 3 wires, the FI computer will set a TP sensor code.

3. Check for a bad fuel injection computer.

   Is there a way to test for a bad FI computer? Yes and no. The only way to test for a bad FI computer is to test it indirectly. This is what I do to test for a bad FI computer (with about a 98% success rate):

   • Eliminate the TP sensor itself as bad.
   • Check the continuity of the 3 TP sensor wires (between the FI computer and the sensor). The idea here is to make that none of the TP sensor wires are cut ('open').
   • Check all of the FI computer 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 FI computer 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 FI computer and sensor), eliminating the FI computer's Ground wires, and verifying the FI computer is getting power on all its power circuits, then, and only then I can say with confidence that the FI computer is bad.

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).