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O2 Sensor Wiring Disaster

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DSM Wiseman
Jun 6, 2011
Colo Spgs, Colorado
Hey guys, I've been attempting to idle tune recently and have gotten nowhere since my front O2 constantly reads .08 volts. I though it was strange since I just installed an OEM O2 sensor. So I started looking at the wires and found this mess.

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There are three white wires going into green sheeths. These wires go to pins 75, 76, and 78 which is Front O2, Rear O2, and Knock Sensor. There are also 5 black wires (one of which is pin 92 Sensor Ground) that are coming from the wiring harness, through the green sheeths, and then the all of the black wires are soldered back to the sheilding inside the sheeths! There is no way this is stock or even okay to leave alone especially since I'm gettin near zero O2 sensor voltage.

So my question is, what do I do with these ground wires? Can I just ground them to the chassis or do they have to be grounded to the ECU? If so, how do I know where each one should go pin wise? There is only a few ground inputs on the ECU, none of which are missing or cut, and what looks like at least 3 stock ground wires that clearly need a better connection.

Any help is appreciated!

BTW these green sheeths go all the way through the wiring harness so even after removing a few feet of shrink wrap I can't find where it ends.
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hold on I got some diagrams for you.

Here check out these pix and see if they don't help. Idk how to physically put a picture in my posts yet so this is best way I know to show you. Let me know if they help or if you need a pic of something else. Computer pin out starts at 1 from top left and ends at 91 or 92 at bottom right. Pictures from Sprint: View Message
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Thanks for that link! It should help me indentify each wire.

But I'm still at a a loss of what to do with the sensor grounds though. And if this is stock it doesn't explain why a brand new OEM O2 sensor reads near 0 at all times.
Honestly, some may not agree, but a ground to me is just that a ground wire. There aren't really different kinds of grounds. Besides the size and type of ground wire really its just a ground. Not like voltage where you may need 5 volts here bat volts here and such. A ground is just a ground so if all else fails and you can't figure out where the stock grounds go you can just chassis ground them. And idk but I'll try and see if i can find that out though I thought they were grounded through the computer but I believe the ecu provides the grounds but doesn't need them to be grounded through it to receive the signal.
Got it figured out. I wired all the black ground wires to pin 92 Sensor Ground and it solved my issue. Front O2 now cycles perfectly as well as the knock sensor functioning (ask me how I know :D) Thanks for the help MJ!
^ Lol because I was getting a couple degrees of rich knock while cruising. A little adjustment of the injectors and it went away.

BTW, if anybody stumbles upon this thread, do you know where to find a good video or wiki on setting up the NB O2 simulation in Link? I can't seem to get mine dialed in.
Yeah I was looking for a way to tune. DSMLink will take your wideband readings and fake an O2 sensor cycle for the ECU. The settings are confusing to say the least and the car just ends up running worse with O2 simulation when my noob self tries to figure it out.

Thanks anyways though.
Wow, your's looked exactly like mine. That's just unacceptable, even from the factory that's 100% laziness and crap. I grounded all of the wires to the sensor ground and the work pretty good. Not to mention now I know where evertyhing is rather than guessing through a grade-A hack job.

Thanks for the link!
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No problem.

I used to make wiring harnesses for ATV's and especially on the Chinese they did that exact same thing. So I did what you did and fixed it all up! Yeah some things that come from the
Just sent a pm but I'm not understanding what ya did. Unless there's something I'm not seeing. The before picture is kinda zoomed in close and there's no "after" picture to see what the difference is. But I thought the black wires in the picture already went to pin 92????? Could you explain in more detail please?
Most of the black wires are the sensor grounds themselves. But rather than grounding to the chassis or the ECU, they're grounded to the green shielding. Then, a couple separate black wires ran from the shielding to the sensor ground at the ECU. I simply ran all of the grounds to Pin 92 Sensor Ground, and grounded the shielding to the chassis.

Although, IIRC this did not fix my issue. I'm glad I did the rewiring for peace of mind, but my voltage issues was elsewhere.
Do you recall where it was? Cause I'm having this issue myself....and you're the only other person I've seen thus far that's had this issue. Pulling my hair out over here.
^ Where what is, that wiring disaster? It's right by the ECU when you pop the kick panel off. It's wrapped in (what looks like) brown packaging tape.

I think my issue was the O2 itself being bad right out of the box.
Where the issue was. Sorry, typo. I haven't been able to get the wideband to work so deleted it and tried a narrowband sensor. Still doesn't work. So trying to find the issue. And I don't see anyone having the issue I'm having. So hard to figure out a solution to it.
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