How To Test The Throttle Position Sensor (1997-2003 4.6L, 5.4L V8 Ford E150, E250, E350)

TEST 2: Making Sure The TPS Is Getting 5 Volts

The second test we'll perform on the TP sensor is to make sure it's receiving power. As you might know, this power comes in the form of 5 Volts DC and is supplied by the PCM.

These 5 Volts are delivered to the TP sensor through the brown with white stripe (BRN/WHT) wire of the sensor's 3-wire connector.

If the BRN/WHT wire is supplying power to your van's TP sensor, your multimeter should show a reading between 4.5 to 5 Volts DC.

After confirming that the TPS is getting power, our final step is to verify that it's receiving Ground.

These are the steps:

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

Up this point, the results of the previous two tests have confirmed that:

• The TPS is not generating a voltage signal that increases or decreases as you open or close the throttle plate (TEST 1).
• The TPS is receiving 5 Volts DC from the PCM (TEST 2).

The next and final test is to verify that the PCM is providing Ground to the throttle position sensor.

The grey with red stripe (GRY/RED) wire of the TP sensor's 3-wire connector is the one that delivers this Ground from the PCM.

We'll use a multimeter to perform a simple voltage test to check for the presence of Ground in the circuit. If the GRY/RED wire is supplying Ground to the sensor, your multimeter should display a reading of 10 to 12 Volts DC.

NOTE: Ground is provided by the PCM, so be careful not to connect this wire to battery power (12 Volts) either intentionally (or accidentally) or you'll fry the PCM. The multimeter voltage test I'm suggesting in the test instructions is a safe way to test for the presence of Ground in this circuit.

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 lets you know the PCM is providing Ground to the TP sensor.

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).

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

TPS Code Won't Go Away

So you've tested the TPS per the instructions in this tutorial, and the results tell you that the TPS is good, but the check engine light is still on. Here are a few suggestions for your next diagnostic steps:

• The throttle plate's idle-stop screw might have been adjusted to mask a misfire or rough idle, causing the engine to idle higher. This adjustment increases 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 binding, preventing the throttle plate from fully closing. You can verify this by having someone inside the vehicle press the accelerator pedal to the floor and release it (with the engine off) while you check that the throttle plate and cable are not getting stuck during their movement.
• The TPS might be failing intermittently, meaning it works fine most of the time but occasionally doesn't. The best way to test for these intermittent issues is to road-test the vehicle with the multimeter connected to the TP signal wire, using a long jumper-wire so you can comfortably observe the signal fluctuations while a helper helps you drive the van on the road.
• The TP sensor's connector might be faulty, often due to a broken locking tab, causing the connector to loosen (as the engine runs) and create an intermittent false connection.