How To Test The TPS (1997-2001 4.0L SOHC Ford Explorer)

TEST 2: Making Sure The TPS Is Getting 5 Volts

The wire that feeds the throttle position sensor with 5 Volts, which are provided by the fuel injection computer, is the brown with white stripe (BRN/WHT) wire of the sensor's electrical connector.

In the photo above, I've labeled this wire with the number 1.

These 5 Volts should be present with the key ON (and of course when the engine is running).

These are the test steps:

1. 1

   Disconnect the TPS from its electrical connector.

2. 2

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

3. 3

   Connect the red multimeter test lead (using the appropriate tool) to the wire labeled with the #1.
   
   This wire will be the brown with white stripe (BRN/WHT) wire of the connector

4. 4

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

5. 5

   Your multimeter should read 4 to 5 Volts DC.

Let's take a look at what your test results mean:

CASE 1: 4 to 5 Volts are present. This is the correct and expected 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: 4 to 4 Volts ARE NOT present. Without this voltage the TP sensor will not produce a TPS voltage signal.

The most likely cause of this missing voltage is an open-circuit problem in the wiring between the TP sensor connector and the fuel injection computer's connector.

Although testing this condition is beyond the scope of this article, you have now eliminated the throttle position sensor (TPS) itself as bad.

TEST 3: Making Sure The TPS Is Getting Ground

So far you have confirmed that:

• The TPS is not producing a voltage signal that increases/decreases as you open/close the throttle plate.
• The TPS is receiving 5 Volts (TEST 2).

For our last test we're gonna' make sure that it's getting Ground.

The wire that feeds Ground to the TP sensor is the wire labeled with the number 3 in the photo above.

This wire is the gray with red stripe (GRY/RED) wire of the sensor's electrical connector.

IMPORTANT: Ground is provided to the TP sensor by your Ford Explorer's fuel injection computer. Be careful and don't connect this wire to battery voltage (12 Volts) or you'll fry the computer. The multimeter voltage test I'm suggesting in the test steps below is a safe way to test for the presence of Ground in the wire.

OK, these are the test steps:

1. 1

   Disconnect the TPS from its electrical connector.

2. 2

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

3. 3

   Connect the black multimeter test lead (using the appropriate tool) to the wire labeled with the #3.
   
   This wire will be the gray with red stripe (GRY/RED) wire of the connector

4. 4

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

5. 5

   Your multimeter should read 10 to 12 Volts DC.

Let's take a look at what your test results mean:

CASE 1: Ground is present. This is the correct and expected test result.

You can conclude that the TPS is bad only if all tests have confirmed that:

1. The TP sensor IS NOT creating a voltage signal that increases/decreases as you open/close the throttle plate.
2. The TP sensor is being fed 5 Volts DC.
3. The TP sensor is being fed Ground.

CASE 2: Ground IS NOT present. Without Ground the TPS will not produce a TPS voltage signal.

The most likely cause of this missing Ground is an open-circuit problem in the wiring between the TP sensor connector and the fuel injection computer's connector. In the extreme of cases, the PCM has an internal problem (although this is very rare).

Although testing this condition is beyond the scope of this article, you have now eliminated the throttle position sensor (TPS) itself as bad.