P0135, P0155 -Upstream O2 Sensor Test (2003-2005 GM 4.8L, 5.3L, 6.0L)

This tutorial will help you to test diagnostic trouble codes P0135 and P0155 on specific 2003, 2004, and 2005 Chevy and GMC Pickups, Vans, and SUVs with either a 4.8L, 5.3L, or 6.0L V8.

If you're wondering if this tutorial applies to your specific 2003-2005 Chevy/GMC pickup, van or SUV... take a look at the ‘Applies To:’ box on the column on the right. If this tutorial doesn't cover your specific vehicle, take a look at the index of tutorials here: O2 Sensor Tutorial Index.

Also, your GM vehicle may use one of two different types of oxygen sensors... depending on where it was built. This tutorial covers both. What's the difference? The difference is in the connector of the oxygen sensor. The photo below will help in identifying them:

Before you start testing/troubleshooting codes P0135 and/or P0155, I recommend that you take a look at the following oxygen sensor tutorial:

  1. Testing P0135, P0141, P0155, P0161 O2 Heater Performance Problem.
    1. This article answers a lot of the most common questions like:
      1. Symptoms Of A BAD oxygen sensor heater element.
      2. Where are the O2 sensors located?
      3. What tools do I need?
      4. What does the heater inside the oxygen sensor do?

Circuit Descriptions Of The Upstream Oxygen Sensors

P0135, P0155 -Upstream O2 Sensor Test (2003-2005 GM 4.8L, 5.3L, 6.0L) P0135, P0155 -Upstream O2 Sensor Test (2003-2005 GM 4.8L, 5.3L, 6.0L) P0135, P0155 -Upstream O2 Sensor Test (2003-2005 GM 4.8L, 5.3L, 6.0L) P0135, P0155 -Upstream O2 Sensor Test (2003-2005 GM 4.8L, 5.3L, 6.0L)

You'll notice that in the photo (in the image viewer), the connectors are identified with either a number 1 or a number 2.

This is because GM uses one of two types of upstream oxygen sensors on your pickup, SUV, or van and depending on which one is installed on your vehicle, the wire colors may be different.

In the circuit descriptions below I've taken this into account and I'll make reference to these numbers (as Type 1 or Type 2) whenever there's a difference in the color of the wire.

Oxygen Sensor Bank 1 Sensor 1 Circuits
Pin Wire Color Description
A Tan HO2S Low Signal
B Purple w/ White stripe HO2S High Signal
C <-> Light Blue Heater Element Ground (Provide by PCM) -Type 1
C <-> Black w/ White stripe Heater Element Ground (Provide by PCM) -Type 2
D Pink Heater Element 12 Volts (O2 sensor fuse)
Oxygen Sensor Bank 2 Sensor 1 Circuits
Pin Wire Color Description
A Tan HO2S Low Signal
B Purple HO2S High Signal
C <-> Purple w/ White stripe Heater Element Ground (Provide by PCM) -Type 1
C <-> Light Green Heater Element Ground (Provide by PCM) -Type 2
D Pink Heater Element 12 Volts (O2 sensor fuse)

TEST INFO: The Basics Of Testing The Oxygen Sensor Heater Element

P0135, P0155 -Upstream O2 Sensor Test (2003-2005 GM 4.8L, 5.3L, 6.0L) P0135, P0155 -Upstream O2 Sensor Test (2003-2005 GM 4.8L, 5.3L, 6.0L) P0135, P0155 -Upstream O2 Sensor Test (2003-2005 GM 4.8L, 5.3L, 6.0L) P0135, P0155 -Upstream O2 Sensor Test (2003-2005 GM 4.8L, 5.3L, 6.0L)

IMPORTANT: Do not test the oxygen (O2) sensor while it's hot or the engine is running (while using the info in this tutorial). Testing a hot O2 sensor can cause severe burns. Be careful and use common sense while testing the oxygen sensors on your vehicle.

OK, keeping the above safety precautions in mind.... in a nutshell, troubleshooting the O2 sensor's heater element requires that you first start by making sure that the oxygen sensor heater element is getting power (10 to 12 Volts) and ground.

  1. Power is provided by the D circuit wire.
    1. This wire will be the Pink one, regardless of the type of O2 sensor GM has installed on your vehicle.
  2. ground is provided by the C wire.
    1. This wire will be one of several colors. To find out which one, you'll need to consult the charts above.

If the O2 sensor is not getting power or ground... then you've found the cause of the P0135 and/or P0155 diagnostic trouble code (since without power and/or ground, the O2 sensor's heater element won't work).

If you do find that the oxygen sensor's heater is getting both power and ground, then the next step, is to measure the resistance (with a multimeter) of the heater element inside the oxygen (O2) sensor to see if it's fried or not.

As you can see, testing DTC's P0135 and/or P0155 is not hard to do at all.... OK, in the next few pages are the step-by-step testing instructions you'll need to get to the bottom of the problem.