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This is a 2005 GMC Yukon 4x4 4.8 L.

Ok, dogs actually ate my harness going to Bank 2 Sensor 1 O2 sensor. The connector from the body side of the wiring is completely gone.

I found a connector I can wire in but am not sure which wires go where.

There are 4 wires on O2 sensor itself:

  • 2 x black
  • 1 x blue
  • 1 x white

Coming off of body wiring harness:

  • 1 x tan
  • 1 x purple
  • 1 x light green
  • 1 x pink

Any help would be greatly appreciated.

  • Welcome to Motor Vehicle Maintenance & Repair! Great lead in to the question! Love it :o) Feb 28, 2018 at 2:01
  • ty Paulster. True story lol
    – Vic S
    Feb 28, 2018 at 2:49

2 Answers 2


Here's what I found:

(Zaid has a good answer, but sometimes on a four wire sensor the ground is floating inside the ECU [as with your Yukon] - which makes his "Step 2" not always reliable. Still, in most cases you could go the "Zaid Route" in the deep woods without power or the internet (a solar soldering iron maybe). Worst case is you would have to flip the WHITE/BLUE if the O2 sensor gave no reading - and nothing would be damaged except your time.)

I am sure of the following:

The two BLACK wires on the replacement are the heater wires. This is a resistance element, so has no polarity. From the wiring diagram, it appears you are dealing with the B2S1 sensor, or the upstream "main" sensor on bank two. For you, that means Pin D "PK" (pink) and Pin C (4.8L) "L-GN" (light green). Connect the two BLACK wires here; the order does not matter.

The BLUE and WHITE wires on the replacement are Sensor+ and Sensor- respectively. That suggests connecting BLUE to PIN B "PU" (purple) for the high side (aka Sensor+), and obviously the remaining WHITE wire connects to PIN A "TN" (tan) for the low side, (aka Sensor-).

Check the following diagrams and see if you come to the same conclusions. The replacement colors I knew, but the Yukon colors were pure mystery. (Some blood has probably crept into my gin stream...)

Good luck!

Generic O2 sensor wire colors

2005 GMC Yukon O2 sensor wiring

Hmmmm. On review, "Zaid Route in the Deep Woods?" Not sure what exactly was thinking... But I swear there were no banjos playing at the time!



This Q&A covers how to determine the sensor-side wiring.


You'll need a multimeter to follow the steps below. This procedure also assumes that the O2 heater circuit functions properly).

  1. Determine the two heater wires

    Set the multimeter to voltage mode (not amperage mode!).

    Start the vehicle with the engine cold. The O2 heater circuit should activate immediately and stay on for a couple of minutes.

    Use this time window to find the two wires out of the four that register a voltage reading. Once located, label or take note of these two wires. Polarity does not matter here.

  2. Determine the ground wire

    Switch the multimeter to resistance mode.

    Of the two wires that remain, test each wire against a known good ground. One multimeter probe connects to the known ground, the other to the wire.

    The ground wire is the one that registers a resistance on the multimeter.

    The other should register as an open loop, and connects to the signal wire on the O2 sensor.

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