How To Test The Throttle Position Sensor (1995-2004 4.6L Crown Victoria, Grand Marquis)

TEST 2: Making Sure The TPS Is Getting 5 Volts

Now that you've confirmed that the TP sensor isn't creating a variable voltage signal, we'll need to check that it's getting 5 Volts DC. As mentioned earlier, these 5 Volts are supplied by the PCM.

It's the brown with white stripe (BRN/WHT) wire of the sensor's 3-wire connector that delivers this voltage and the one that we're gonna test in this section.

If the BRN/WHT wire is supplying power to the TP sensor, you'll see a reading of 4.5 to 5 Volts DC on your multimeter.

Let's get started:

1. 1

   Disconnect the TP sensor from its 3-wire connector.

2. 2

   Connect the black multimeter test lead 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 1 with the red multimeter test lead (see photo above).
   
   This female terminal should connect to the BRN/WHT wire of the 3-wire connector.

6. 6

   Your multimeter should read 4.5 to 5 Volts.

Let's analyze your test results:

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

The next step is to make sure that the TPS is getting Ground. For this test go to: TEST 3: Making Sure The TPS Is Getting Ground.

CASE 2: The multimeter DID NOT register 4.5 to 5 Volts. This result tells you that the TP sensor is not getting the power it needs to function.

This missing voltage is generally the result of an open-circuit problem in the the BRN/WHT wire or the PCM is fried (not very common).

Altho testing these two conditions is beyond the scope of this tutorial, you have now eliminated the throttle position sensor (TPS) itself as faulty.

TEST 3: Making Sure The TPS Is Getting Ground

So far, the results of the previous two tests have confirmed:

• The TPS isn't producing a voltage signal that changes as you open or close the throttle plate (TEST 1).
• The TPS is getting 5 Volts DC from the PCM (TEST 2).

For our final TP sensor test, we'll check that the grey with red stripe (GRY/RED) is supplying it with Ground.

A simple multimeter voltage test will do to help us confirm that Ground is present in the GRY/RED wire.

NOTE: The PCM provides this Ground, so be careful not to connect this wire to battery power (12 volts), whether intentionally or accidentally, as this will damage the PCM. The multimeter voltage test I'm recommending in the instructions is a safe way to check for Ground in the GRY/RED wire.

OK, let's start:

1. 1

   Disconnect the TP sensor from its 3-wire connector.

2. 2

   Connect the red multimeter test lead 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 3 with the red multimeter test lead (see photo above).
   
   This female terminal should connect to the GRY/RED wire of the 3-wire connector.

6. 6

   Your multimeter should read 4.5 to 5 Volts.

Let's interpret your test results:

CASE 1: The multimeter registered 10 to 12 Volts. This test result confirms the TP sensor is being supplied with Ground (from the PCM).

You can conclude that the TPS is bad and needs to be replaced if you have:

• Confirmed the TPS is not producing a voltage signal that increases/decreases as you open/close the throttle plate (TEST 1).
• Confirmed the TPS is getting 5 Volts DC from the PCM (TEST 2).
• Confirmed the TPS is getting Ground from the PCM (this test section).

CASE 2: The multimeter DID NOT register 10 to 12 Volts. This test result lets you know that the TPS is not getting Ground.

This missing Ground is generally the result of an open-circuit problem in the the GRY/RED wire or the PCM is fried (not very common).

Although testing these two conditions is beyond the scope of this tutorial, you have now ruled out the throttle position sensor (TPS) itself as the problem.

TPS Code Won't Go Away

If the TP sensor tested good or you've replaced it, but the TPS diagnostic trouble code keeps coming back and illuminating the check engine light, I've compiled a list of possible issues that could be causing this problem:

• The throttle plate's idle-stop screw might've been adjusted to 'solve' a misfire or rough idle condition, leading to a higher idle speed. This adjustment raises the TP sensor's signal to the PCM, which doesn't like it and triggers the check engine light (CEL).
• The throttle cable could be sticking, stopping the throttle plate from fully closing. You can check this by having a helper step on and off the accelerator pedal (with the engine off) while you check the throttle plate and cable's movement.
• The TPS may be failing intermittently. What I mean is that it may work fine most of the time but occasionally it may stop generating a variable voltage signal.
  
  The best way to check for these intermittent problems is by road-testing the vehicle with the multimeter connected to the TP signal wire, using a long jumper-wire so you can comfortably watch the signal changes while someone else drives.
• The TP sensor's connector is damaged. The most common problem is that its locking tab has broken off, causing the connector to loosen while the engine runs and creating an intermittent false connection.

More 4.6L Crown Victoria And Grand Marquis Tutorials

If this tutorial was helpful, be sure and take a look at all of the 4.6L Ford Crown Vic and Mercury Grand Marquis diagnostic tutorials and wiring diagrams in this index:

• 4.6L Crown Victoria And Grand Marquis Index of Articles.

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

• How To Test Engine Compression (1992-2011 4.6L Crown Victoria, Grand Marquis).
• Blown Head Gasket Tests (1992-2011 4.6L Crown Victoria, Grand Marquis).
• How To Test The Fuel Injectors (1992-1997 4.6L Crown Victoria, Grand Marquis).