O2 sensor harness wire colors
Thread Starter
Racer
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From: Fort Lauderdale , Fl
One is a ground and the other is another wire for the heater element.
So is W a ground?
Or is BR a ground?
Racer
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From: CA
I admit I stood back and watched this thread thinking it is so straightforward that it would be no problem. I can't understand why four wires to the ECU are causing the poor guy such a headache. Where in the hell did they cut his harness? I really would like to see a picture of this mess since I doubt the O2 sensor would have been damaged if it was never hooked up correctly.
Paul
Paul
Racer
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From: CA
Thread Starter
Racer
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From: Fort Lauderdale , Fl
Thats what I thought, so based on that and all these diagrams I now have the wiring hooked up correctly. But for some reason still getting o2 sensor codes with a brand new sensor.
I’ll have to get a pic later as my wife has the car right now. But regardless, it’s wired “correctly” based on all the info here.
I do appreciate all the help guys, I just don’t understand how this is creating such an issue.
And on top of it all, the last guy cut all the engine harness wires so short that to redo his wiring mess it all had to be done in the little space between the firewall and the back of the engine.
I’ll have to get a pic later as my wife has the car right now. But regardless, it’s wired “correctly” based on all the info here.
I do appreciate all the help guys, I just don’t understand how this is creating such an issue.
And on top of it all, the last guy cut all the engine harness wires so short that to redo his wiring mess it all had to be done in the little space between the firewall and the back of the engine.
Lead Lap
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From: Texas
Racer
Joined: Aug 2019
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From: CA
Good lord! What kind of idiot was that guy? Sheesh. I truely am sorry for the problems you are having, but the code being thrown may be related to something else with a mess like that. The ECU has so many things tied to it and Toyota/Lexus will not release their S/W diagnostic tree to know exactly which input to the ECU is bad. I know, I have tried.
This sounds extreme. But I would find a replacement harness on ebay or you may have issues like this for years.
Paul
This sounds extreme. But I would find a replacement harness on ebay or you may have issues like this for years.
Paul
Racer
Joined: Aug 2019
Posts: 1,757
Likes: 355
From: CA
If his entire harness or even just the O2 sensor wires coming up next to the firewall has been cut, all bets are off here. It could be a short if it was improperly spliced. It could be a lot of things. Like I suggested, I would go on ebay or my local salvage yard and replace that portion of the harness then worry about the sensor which is apparently not affecting the ability to drive the car. Gas mileage most likely is compromised. His biggest issue is probably passing inspection.
Paul
Paul
Last edited by Raven01750; Jun 20, 2020 at 09:10 AM.
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Lead Lap
Joined: Aug 2006
Posts: 4,759
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From: Texas
If his entire harness or even just the O2 sensor wires coming up next to the firewall has been cut, all bets are off here. It could be a short if it was improperly spliced. It could be a lot of things. Like I suggested, I would go on ebay or my local salvage yard and replace that portion of the harness then worry about the sensor which is apparently not affecting the ability to drive the car. Gas mileage most likely is compromised. His biggest issue is probably passing inspection.
Paul
Paul
Thread Starter
Racer
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From: Fort Lauderdale , Fl
Also have a new o2 sensor in the mail so we’ll see if the current one is bad.
The o2 I pulled off the car the other day looked to be almost new so that one may still be good too if this wiring nonsense was the issue.
Bgw, I haven’t tested any of them... lost my meter a while back and never got around to a new one. I know, I know.
I wonder if driving a few miles for the test drive with the sensor wired in assbackwards was able to damage the sensor.
Last edited by CCC-TT; Jun 20, 2020 at 10:58 AM.
Lexus Test Driver
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From: Fl
Thread Starter
Racer
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Joined: Feb 2007
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From: Fort Lauderdale , Fl
Pole Position
Joined: Jan 2020
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From: CA
Be careful when you ohm out the heater circuit of your O2 sensor. I notice the diagrams on the second photo don't match the diagrams on the third photo. The pin numbering on the O2 sensor connector appears to be wrong on the page (second photo) that illustrates how to check the ohms. I only have the 2008 shop manual, so I can't advise, but according to my book, looking at the open-end of the connector, with the locking mechanism on top, the pin numbering should be:
2 1
4 3
This matches the diagram on the third photo as well (and also matches my 2008 book).
In my book, you check the heater across pins 1 and 2 (both black wires on the Denso O2 sensor).
From what I can gather looking at the thread and photos above, and going by the O2 sensor connector pin numbering above (in this message) your wiring should be:
1 HT (heater ground via the ECM)
2 +B (heater positive)
3 OX (shielded control wire going to ECM)
4 E1 (non-shielded control wire going to ECM)
2 1
4 3
This matches the diagram on the third photo as well (and also matches my 2008 book).
In my book, you check the heater across pins 1 and 2 (both black wires on the Denso O2 sensor).
From what I can gather looking at the thread and photos above, and going by the O2 sensor connector pin numbering above (in this message) your wiring should be:
1 HT (heater ground via the ECM)
2 +B (heater positive)
3 OX (shielded control wire going to ECM)
4 E1 (non-shielded control wire going to ECM)
Pole Position
Joined: Jan 2020
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From: CA
My guess is that you could fry the O2 sensor within seconds of applying voltage to non-heater side of it. Pray that the botched wiring by the previous mechanic didn't fry the ECM as well.