Right Front O2 Sensor (HO2S11) Heater Test (1997-1999 F150 - F250)

This tutorial will help you troubleshoot a right front oxygen sensor (HO2S11) heater circuit performance problem... usually accompanied by the following diagnostic trouble code lighting up the check engine light on the instrument panel:

  1. P0135: Heated Oxygen Sensor (HO2S-11) Circuit Malfunction.

Testing the oxygen sensor for a heater circuit malfunction is pretty easy (the hard part may just be jacking up your Ford on jack stands and trying to get to it). Once you do get to it, I'll show you how to test it in a step-by-step manner in the following pages.

By the way, your Ford pickup has a total of 4 oxygen sensors (if it's equipped with dual exhaust). This tutorial focuses on testing the right front oxygen sensor's heater. All four oxygen sensor's are tested in the exact same manner... the only thing that changes is the color of the wires sticking out of the oxygen sensor's engine wiring harness connector.

Here are the contents of this tutorial at a quick glance:

  1. Right Front Oxygen (HO2S11) Sensor Circuit Descriptions
  2. TEST 1: Making Sure O2 Sensor Heater is Getting Power.
  3. TEST 2: Making Sure O2 Sensor Heater is Getting Ground.
  4. TEST 3: Checking the O2 Heater's Resistance.
  5. Oxygen Sensor Locations.
  6. Where to Buy the Oxygen Sensor and Save.
  7. More Ford 4.6, 5.4L Tutorials.

En Español You can find this tutorial in Spanish here: Calentador del Sensor de Oxígeno -P0135 (1997-1998 F150-F250) (at: autotecnico-online.com).

NOTE: This tutorial covers only the 1997-1998 Ford F150 and F250 equipped with a 4.6L/5.4L V8 engine.

The following tutorial may also be of help:

  1. Left Front O2 Sensor (HO2S21) Heater Test (1997-1998 F150 - F250).

Right Front Oxygen (HO2S11) Sensor Circuit Descriptions

Right Front Oxygen (HO2S11) Sensor Circuit Descriptions

You'll notice, once you get into the test, that I'm gonna' refer to two different connectors. These are:

  1. Oxygen sensor engine wiring harness connector.
  2.       -and-
  3. Oxygen sensor connector.

The difference may seem pretty obvious, but just to make sure: The O2 sensor engine wiring harness connector is the connector that belongs to the entire wiring harness of your Ford's engine. Also, this connector has round female terminals.

When I simply refer to the O2 sensor connector, I'm referring to the connector that belongs to the oxygen sensor itself. The oxygen sensor connector has round male terminals.

OK, all of the four oxygen sensors on your Ford are pretty much identical. The only difference in them, besides their location on the exhaust and engine bank, is the color of the wires of the O2 sensor engine wiring harness connector they plug into.

Below is a description of the wires of the right front oxygen sensor (HO2S11):

Right Front O2 Sensor (HO2S11) Circuit Descriptions
Pin Wire Color Description
1 RED VPWR -12 Volts
2 RED/WHT Heater GND -Heater Ground Provided Internally by the PCM
3 GRY/RED O2 SIG RTN -Sensor Signal Ground
4 YEL/RED O2 SIG -Oxygen Sensor Signal

NOTE: The right front oxygen sensor is located on the right side (passenger side) of the engine. It's the O2 sensor before the catalytic converter. To further help you in locating the right front oxygen sensor (HO2S11), take a look at the section: Oxygen Sensor Locations.