How To Diagnose And Resolve DTC P0141 (1997-2000 4.2L V6 Ford E150, E250)

TEST 2: Making Sure The Heater Element Is Getting Ground

Now that you've checked and confirmed that the O2 sensor's heater element is getting power, we now need check that it's also getting Ground.

This Ground, which as the activation signal for the heater element, is provided by the the PCM when the key is turned to the RUN position.

The wire that delivers Ground to the O2 sensor's heater element is the yellow with light blue stripe (YEL/LT BLU) wire of the sensor's 4-wire engine wiring harness connector.

Let's get testing:

1. 1

   Disconnect the O2 sensor from its engine wiring harness connector.

2. 2

   Place your multimeter in Volts DC.

3. 3

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

4. 4

   Turn the key to the RUN position but don't crank or start the engine.

5. 5

   Gently probe the female terminal of the connector that connects to the YEL/LT BLU wire with the black multimeter test lead.
   
   NOTE: This test is done on the O2 sensor's 4-wire engine wiring harness connector. This connector has female terminals.

6. 6

   Your multimeter should register 10 to 12 Volts DC.

Let's interpret your test result:

CASE 1: The YEL/LT BLU wire is delivering 10 to 12 Volts. This is the correct and expected test result.

Your next step is check that the heater element is getting Ground. Go to: TEST 3: Testing The Heater Element's Resistance.

CASE 2: The YEL/LT BLU wire IS NOT delivering 10 to 12 Volts. Without this voltage, the heater element will not function.

If the engine in your van starts, the most likely cause of this missing voltage is an open-circuit problem between the engine wiring harness O2 sensor connector and the PCM Power Relay.

TEST 3: Testing The Heater Element's Resistance

So far, you have:

• Verified that the O2 sensor's heater element is receiving 10 to 12 Volts (TEST 1).
• Checked that the O2 sensor's heater element is receiving Ground (TEST 2).

In this final test section, we'll measure the resistance of the oxygen sensor's heater element using a multimeter set to Ohms mode.

If the heater element is problem-free, your multimeter should display a resistance value ranging from 3 to 30 Ohms (at room temperature).

NOTE: This measurement should be taken at the oxygen sensor's connector, which features round male terminals.

OK, these are the test steps:

1. 1

   Disconnect the O2 sensor.

2. 2

   Locate the male terminals labeled with the number 1 and number 2 of the O2 sensor connector itself (not the engine wiring harness O2 connector).
   
   NOTE: This connector has male terminals and belongs to the O2 sensor itself.

3. 3

   Place your multimeter in Ohms mode.

4. 4

   With your multimeter in Ohms mode probe terminals number 1 and number 2 of the O2 sensor's connector.

5. 5

   If all is OK, you should see about 3 to 30 Ohms (Ω) on your multimeter.
   
   If the heater element is fried, your multimeter will show an open (usually indicated by the letters OL) or a number over 10 K Ω.

Let's take a look at your test results:

CASE 1: The oxygen sensor's heater resistance is within specification. This is the correct test result and tells you the oxygen sensor's heater element is OK.

CASE 2: The oxygen sensor's heater resistance IS NOT within specification. This confirms that the HO2S-21 sensor's heater element is fried.

You can conclude the HO2S-21 sensor is bad and the cause of the P0141 trouble code if you have:

• Confirmed that the sensor's heater element is getting power (TEST 1).
• Confirmed that the sensor's heater element is getting Ground (TEST 2).
• In this test you have confirmed that the heater element's resistance is not within the indicated specification.

Taking all of the above into account you can correctly conclude that the sensor needs to be replaced with a new one.

More 4.2L Ford E150 And E250 Test Tutorials

If this tutorial was helpful, be sure and take a look at all of the 4.2L V6 E150 and E250 diagnostic tutorials and wiring diagrams in this index:

• 4.2L Ford E150 And E250 Index of Articles.

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

• How To Test The Throttle Position Sensor (1997-2000 4.2L V6 Ford E150, E250).
• How To Test Engine Compression (1997-2003 4.2L V6 Ford E150, E250).
• How To Test The Fuel Pump (1997-2000 4.2L V6 Ford E150, E250).
• How To Test The CKP Sensor With A Multimeter (1997-2003 4.2L V6 Ford E150, E250).