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E46 M3 (2001-2006) Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006.


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Old Sun, Jan-08-2017, 01:37:35 PM   #121
maruscmn
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Default Re: Extending O2 wiring for Section 1 with Cats

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Originally Posted by mikerob View Post
I am referring to the pic above where the two harnesses are side by side. Maybe this was addressed elsewhere, but would it be possible to just extend the two secondary O2 sensor wires in the USA harness so they are the same length and the Euro counterpart? Then re-bundle the wires to mimic the Euro harness?
This is all I did. Rewrapped the wires. Looks stock.
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Old Sun, Jan-08-2017, 01:57:19 PM   #122
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Default Re: Extending O2 wiring for Section 1 with Cats

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Originally Posted by maruscmn View Post
This is all I did. Rewrapped the wires. Looks stock.
I may try this approach first - if I am not happy with it, I'll buy the O2 harness.

Question for terraphantm.
I noticed in your posts you show a very nice crimp that you made when splicing wires. Do you prefer crimping over soldering? What brand / model crimping tool do you use?
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Old Sun, Jan-08-2017, 03:03:01 PM   #123
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Default Re: Extending O2 wiring for Section 1 with Cats

Yeah I generally prefer crimps, and I've always read that crimping is preferred to soldering for O2 sensors.

I think I used this one back then, nothing special: http://hep.ucsb.edu/people/sburke/AmpChamp.pdf

There are better crimp tools you can use, but if you're careful the crimps turn out fine. Still working great 2 years later
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Old Sun, Jan-08-2017, 06:11:42 PM   #124
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Default Re: Extending O2 wiring for Section 1 with Cats

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Originally Posted by terraphantm View Post
Well I did some digging around and this is what I've found:

US O2 Sensors:
Precat Bank 1: 11781743994 L=840MM = C
Precat Bank 2: 11781405324 L=750MM = A

Postcat Bank 1: 11781406621 = 1075MM = A
Postcat Bank 2: 11781406622 = 935MM = B


Euro O2 Sensors
Precat Bank 1: 11781743994 L = 840MM (SAME AS US) = C
Precat Bank 2: 11781406622 L = 935MM (SAME AS US POST CAT BANK2) = B

Postcat Bank1: 11781405324 L = 750MM (SAME AS US PRECAT BANK2) = A
Postcat Bank2: 11787832035 L = 480MM (UNIQUE) = C

So it's easy enough to get 3 out of the 4 sorted with the proper wires. For the last one I have a couple choices. Buy another precat bank 1 sensor and shove the extra length somewhere. Or buy the Euro piece

I was also looking at swapping the connectors at the harness side, but the pins don't seem to be removable non destructively.
You can actually buy the O2 sensor plugs separately:

Plug A = 12521703571
Plug B = 12521740485
Plug C = ? (couldn't find but don't need)



I haven't figured out how to pop the wires out yet, but if you swapped the plugs on the Euro sensors like this, would the Euro sensors reach using the US wiring harness our would you need to switch to the Euro harness as well?

Euro O2 Sensors
Precat Bank 1: 11781743994 L = 840MM (SAME AS US) = C (No change)
Precat Bank 2: 11781406622 L = 935MM (SAME AS US POST CAT BANK2) = B >> A

Postcat Bank1: 11781405324 L = 750MM (SAME AS US PRECAT BANK2) = A (No Change)
Postcat Bank2: 11787832035 L = 480MM (UNIQUE) = C >> B

Its a little counterintuitive to me that the Euro post-cats are shorter than the US post-cats but since I bought the euro spec sensors, it would be cheaper for me to switch plugs on 2 sensors (if that will work) than it would be to buy a new 11781406621 (assuming I stay with the original plan of replacing all sensors).

[EDIT: Disregard, I answered my own question. You do need the Euro Harness with the Euro Sensor lengths. I'm better off just staying all US-Spec and buying a 11781406621 and calling it a day].

Last edited by TMSNYC; Sun, Jan-08-2017 at 06:45:32 PM. Reason: Problem solved.
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Old Sat, Apr-01-2017, 08:27:35 PM   #125
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Default Re: Extending O2 wiring for Section 1 with Cats

I just did the rerouting of EGT and Post-Cat O2 sensors this morning, OP thank you SOOOO much for writing all this down and taking pictures. It was invaluable with rerouting these o2 sensor cables/wires. (Installing Euro headers and cats). Had the Headers coated by Swaintech / White lightning recently:



-Ben
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Old Sat, Apr-15-2017, 11:57:26 PM   #126
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Default Re: Extending O2 wiring for Section 1 with Cats

Since so many folks have been interested in how to solve the US harness / Euro section 1/cats o2 wire issue, I'm posting my solution. I ended up doing what the OP suggested with cutting OEM up top wire loom, and pulling post cat O2's out, and rerouting EGT/Post cat wires down driver's side underneath the intake manifold. As far as a place to mount the EGT connector and Post cat O2 sensor connectors, I ended up picking up the Euro bracket (part # 11787831183, if you have issues obtaining this, please contact me and I can connect you with the guy that helped me, an associate of Murray Motorsports in Ireland), which, just like the OP, my cables didn't reach it... So, I improvised. I cut the bracket into two pieces, and only used the parts i needed:









And while not pretty, here's my final solution installed



In short, I used those two pieces installed on the rear stud near the fuel filter area along with one of the plastic screws folks have mentioned, BMW part # 16131176747). I used another of those plastic screws, and a 5/8 clamp from Home depot (see below) to clamp the EGT connector into place down there as well).

5/8 in. Rubber Insulated Metal Clamps (2-Pack)
http://www.homedepot.com/p/5-8-in-Ru...7792/100130546

I don't have any pictures of the metal clamps I used to keep the post cat wires off of the exhaust, but this is the part number, obtained from the dealer:

Metal Clips (needed 4-5)
BMW Part # 12521437136

Both the plastic screws and these metal clips were not in stock at my dealerhsip, and took 3-5 business days for them to obtain.

Feel free to message me if folks have any questions as I just finally took it for the final test drive, so far so good! (no codes), may have an exhaust leak between Euro sect 1 -> SGT Sect 2, but if the case, is due to some used euro cats (sect 1) that I picked up where the flanges weren't in the perfect position, so I had to really work on tigthening order of exhaust parts to 'try' to fix the issue, not sure yet if I succeede Anyway, take care all!

Last edited by TheTrackDude; Sun, Apr-16-2017 at 12:01:41 AM.
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Old Mon, Jun-19-2017, 02:35:36 AM   #127
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Default Re: Extending O2 wiring for Section 1 with Cats

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Originally Posted by terraphantm View Post

Confirmed. I worked on a Euro spec yesterday and sure enough:



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Old Mon, Jun-19-2017, 06:10:33 AM   #128
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Default Re: Extending O2 wiring for Section 1 with Cats

Nice. I'll have to order a couple next time I need some BMW parts.
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Old Fri, Jun-30-2017, 11:31:11 AM   #129
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Default Re: Extending O2 wiring for Section 1 with Cats

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Originally Posted by kaiv View Post
Confirmed. I worked on a Euro spec yesterday and sure enough:



So, why are these needed? Is there a reason to raise the cover when rerouting the O2 sensors. I am assuming 4 of these are required?
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Old Fri, Jun-30-2017, 12:02:34 PM   #130
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Default Re: Extending O2 wiring for Section 1 with Cats

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Originally Posted by mikerob View Post
So, why are these needed? Is there a reason to raise the cover when rerouting the O2 sensors. I am assuming 4 of these are required?
See post #89. only 2 required.
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Discussing Extending O2 wiring for Section 1 with Cats in the E46 M3 (2001-2006) Forum - Engine: S54 - Max Hp: 333 hp at 7,900 rpm / 262 lb/ft at 4,900 rpm
Total Produced: 45,000+ - Years Produced: 2001 to 2006. at BMW M3 Forum.com (E30 M3 | E36 M3 | E46 M3 | E92 M3 | F80/X)