Oxygen Sensor Heater Test -P0135 (1997-1998 4.2L V6 Ford F150, F250)

Troubleshooting diagnostic trouble code (DTC) P0135: HO2S 11 Circuit Malfunction is not as hard as you might think. The cool thing is that you don't need any expensive diagnostic test equipment, all you'll need is a multimeter.

A trouble code P0135 tells you that the internal oxygen sensor heater for the right front oxygen sensor has a problem. This usually happens when the heater (inside the right front O2 sensor) goes bad.

In this tutorial, I'll show you the 3 basic tests you'll need to perform to diagnose the right front oxygen sensor.

You can find this tutorial in Spanish here: Probando El Código P0135 (1997-1998 4.2L V6 Ford F150 And F250) (at: autotecnico-online.com).

APPLIES TO: This tutorial applies to the following vehicles:

• 4.2L V6 Ford F150: 1997, 1998.
• 4.2L V6 Ford F250: 1997, 1998.

WIRING DIAGRAM: The oxygen sensor circuit wiring diagram can be found here:

• Oxygen Sensors Circuit Wiring Diagram (1997, 1998 4.2L V6 Ford F150, F250)

P0141 DIAGNOSTIC TESTS: If you need to troubleshoot a P0141 DTC (the left front O2 sensor -HO2S 21), take a look at the following tutorial:

• Oxygen Sensor Heater Test -P0141 (1997-1998 4.2L F150, E150, E250).

E-SERIES VANS: The P0135 diagnostic tutorial for the 1997-1998 4.2L V6 Ford E150/E250 vans can be found here:

• How To Diagnose And Resolve DTC P0135 (1997-2000 4.2L V6 Ford E150, E250)

What Does Trouble Code P0135 Mean?

Here's the nitty-gritty of diagnostic trouble code P0135 and the info you need to troubleshoot it:

P0135: Heater Circuit Malfunction (Bank 1, Sensor 1)

• What Does It Mean: This code tells you that there's a problem with the heater circuit of the oxygen sensor located upstream from the catalytic converter on the side of the engine where the number 1 cylinder is.
• Bank 1 Sensor 1 (B1S1) Location: This oxygen sensor is located on the exhaust manifold that's bolted to the right (passenger) side of the engine. This side of the engine is known as 'Bank 1' and it houses cylinders 1, 2, and 3.
  
  This O2 sensor measures the oxygen content of the exhaust gas as it exits cylinders 1, 2 and 3 and before it passes through the catalytic converter. The powertrain control module (PCM) uses this info to fine-tune in real-time the air/fuel mixture for the three cylinders that make up Bank 1.
• Other Designations: This particular O2 sensor goes by different names. Here are the most common ones you'll come across:
  • Upstream Right Oxygen Sensor.
  • Right Side Upstream Oxygen (O2) Sensor.
  • Passenger Side Front Oxygen Sensor.
  • Right Front O2 Sensor.
  • Right Front Heated Oxygen (O2) Sensor.
  • Bank 1 Pre-Catalytic Converter Oxygen Sensor.
  • HO2S 11.
  • Oxygen Sensor Bank 1 Sensor 1.
• Possible Causes:
  • Faulty oxygen sensor (Bank 1, Sensor 1).
  • Damaged wiring or connector to the sensor.
  • PCM malfunction (less common).

How To Resolve Trouble Code P0135

For most folks, the go-to solution for DTC P0135 is replacing the oxygen sensor it's accusing of having a heater circuit problem. Here are the three main reasons why:

• O2 Sensor Is Easy to Replace: Replacing the O2 sensor isn't difficult. You don't need any fancy or expensive diagnostic equipment or specialized skills, just an O2 sensor socket/wrench tool.
• O2 Sensor Is Not Expensive: Compared to other engine management system components, O2 sensors are pretty inexpensive, typically costing around $30 to $50. This makes replacing it the go-to solution for many folks.
• Lack of Diagnostic Experience: Troubleshooting the heater circuit does take time and, in some cases, requires a professional-grade scan tool (the ones that run $3,000 or more). Not only that, you may need access to professional diagnostic information.
  
  For most folks (even some repair shops), it's more practical to replace the sensor right off the bat. The thinking here is that it's not very common to have other issues, such as electrical wiring problems in the O2 sensor heater circuit.

If you want to skip testing the O2 sensor's heating element and just replace it, I have one important suggestion:

• Inspect Wiring Harness: Visually inspect the oxygen sensor's wires (both the wires coming out of the sensor and the engine wiring harness wires to that connect to them). Look for any signs of damage, such as melted insulation or wires that are shorted together.
  
  Damaged wiring can cause the engine not to start. This is because the fuse that supplies power to the O2 sensor's heating element also powers the fuel pump, fuel injectors, and ignition coil. A short circuit in the O2 sensor wiring could blow this fuse.
  
  If you find any issues with the wiring, address them before installing a new oxygen sensor.

To see my oxygen sensor recommendations and where to buy them, go here: Where To Buy The O2 Sensor And Save.

Circuit Descriptions Of The Upstream Oxygen Sensor

The right front heated oxygen sensor (HO2S 11), on your 4.2L V6 equipped F150 (F250) is a 4 wire oxygen sensor.

2 wires are for actual oxygen sensing part. The other 2 are to supply the heater with power and Ground.

NOTE: You can find the location of the right front oxygen sensor (HO2S 11) here: Location Of The Oxygen Sensors.

Below, you'll find the color of the wires of the engine wiring harness oxygen sensor connector for sensor HO2S 11:

Pin	Wire Color	Description
1	RED/WHT	Heater Ground (-)
2	RED	Heater Power (+)
3	GRY/RED	O2 Signal Ground
4	GRY/LT BLU	O2 Signal

Where To Buy The Oxygen Sensor And Save

If you find, after testing the upstream oxygen sensor that its heater element is fried, take a look at the links below. I think they'll save you some bucks:

NOTE: If you're not sure if the above O2 sensor fit your particular 4.2L V6 equipped F150 (F250) don't worry, once you get to the site, they'll make sure the sensor is the right one, if not, they'll find you the right one.

TEST 1: Verifying The Heater Element Is Getting Power

The first order of business is to check that the right front oxygen sensor (HO2S 11) is getting power (10 to 12 Volts DC).

Of the 4 wires sticking out of the engine wiring harness O2 sensor connector, it's the red (RED) wire that feeds power to the HO2S 11 heater element.

CAUTION: The O2 sensor can get and stay very hot! Perform this test with a completely cold engine. Be careful and take all necessary safety precautions! Also, if you raise your vehicle with a jack, place it on jack stands.

IMPORTANT: The illustration of the connector above is of the engine wiring harness O2 sensor connector. This connector has female terminals.

OK, this is what you'll need to do:

1. 1

   Disconnect the O2 sensor from its engine wiring harness connector.

2. 2

   Place your multimeter in Volts DC.

3. 3

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

4. 4

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

5. 5

   With the red multimeter test lead, probe the male terminal of the connector that connects to the RED wire of the O2 sensor's 4-wire connector.

6. 6

   Your multimeter should register 10 to 12 Volts DC.

Let's take a look at your test results:

CASE 1: Your multimeter confirms that the RED wire is delivering 10 to 12 Volts DC. This confirms that the right front oxygen sensor's heater element is getting power.

The next step is to make check that the RED/WHT wire, of HO2S 11 engine wiring harness connector, is feeding Ground to the heater element. For this test, go to: TEST 2: Verifying The Heater Element Is Getting Ground.

CASE 2: Your multimeter confirms that the RED wire IS NOT delivering 10 to 12 Volts DC. Re-check that you're testing the correct wire and that the key is in the RUN position (but don't crank or start the engine) and re-test.

If your multimeter still does not register 10 to 12 Volts DC, then you can conclude that HO2S 11 itself IS NOT bad since without power, the heater element won't work.

Although it's beyond the scope of this article, the next step is to find out why this battery power is missing using a wiring diagram.