# Need HELP with o2 sensor wiring to ECU



## KyleNorris (Jul 19, 2005)

At some point the pigtail harness connectors for my O2 sensors got ripped off. I was able to find a replacement set of connectors but the wires coming out of them are different colors than the wires on the cars harness.

Does anybody have a wiring diagram for what color wires go to what position on the 4-pin and 6-pin O2 sensor connectors on a 2003 1.8T GTI? Even a closeup picture of the 4 and 6 pin connectors with the wires would be helpful. It seems that different years (or maybe engines) had different wire colors. After checking out a Bently manual i downloaded i cant find anything showing the wires coming from the ECU being the same colors as the ones on the car. Im seeing two red/white wires and two of the thicker lilac/red wires, but cant find that setup anywhere in a wiring diagram for that part of the vehicle. Pics below.

I'm getting real frustrated trying to figure out what to splice where and really need to get this together. Any help would be greatly appreciated.


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## KyleNorris (Jul 19, 2005)

bump?


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## AmIdYfReAk (Nov 8, 2006)

What year/model car are you using?

And what year/model did the replacement harness come out of?

Give me that information and I'll see what i can find.

Edit: Easier than i figured...


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## KyleNorris (Jul 19, 2005)

Thanks! the car is an 03 GTI 1.8t. The harness connectors i am not sure as they had to be bought on ebay and of course were listed as a golf/jetta 02-05. Apparently VW only sells the plastic connector part and nothing with pins or wires so that is the route i had to go. That chart actually looks like right. Did you just whip that up?


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## AmIdYfReAk (Nov 8, 2006)

Ah, VW uses the wideband ( 6 pin ) 0/2's on lots of cars. 

They'll sell you the plastic housing, then "repair" wires for the 5 required connections... Last i priced it out it was something like $12 for the housing, and $9 for each wire. No thanks. 

And does it matter? Repair away! The locations are labeled in the plastic housing, make sure you pin it correctly.. and with any luck they didn't short taking out the ECU's throttle control.


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## KyleNorris (Jul 19, 2005)

Ive been driving it like this for a couple of months (no garage, **** Chicago weather) and its been running a little rough but not awful. Question, on the post cat do you think its possible to just skip the harness connections and splice it direct or is there some sort of resistance it needs from the pins? Reason being is that most of the post cat sensors just come with the 4 wires and no plug, so while i have the ECU end of that plug, and the pre-cat came with the correct connector, the connector that i can use from the post-cat sensor is pretty ****ed from dragging.

Thanks again, you saved me one of those expensive awkward visits to the dealership where they lecture me about running with a test pipe and aftermarket anything.


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## AmIdYfReAk (Nov 8, 2006)

To be as blunt as possible, You could splice the rear o/2 directly into the factory wiring and it would work flawlessly... But that has to be one of the biggest ******* moves i can think of doing in this situation. 

Pin it with the connections you've got, and worse comes to worst, use a Zip and put it in the middle of the connector to hold the damaged side and harness side together and tuck it away until you replace the rear o/2 or source a new plastic housing.


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## Izan (Jan 24, 2016)

AmIdYfReAk said:


> What year/model car are you using?
> 
> And what year/model did the replacement harness come out of?
> 
> ...




Hi, hope you can assist, I have the exact color code on my 4-wire o2 sensor plug, I need the pinout from that to the ECU? Really hope you can assist?


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