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      02-06-2010, 12:18 PM   #1
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How difficult would it be to extend one set of O2 sensors?

Just wondering how difficult it would be to extend the second set of O2 sensors to behind the secondary cats? Wouldn't it just be splicing a longer wire to the secondary O2 wire?
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      02-06-2010, 01:34 PM   #2
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I asked about that the other day and never got much of a response, but I think the answer is yes, you can splice in a comparable gauge wire and extend them. As far as I can tell no one makes a plug and play extender harness like they do for many GM cars, etc. I'm not sure how you would go about routing the extra wire though. Does the heat shielding in the top of the tunnel area come out so the extra wire could be placed behind it rather than between it and the exhaust? If not I'm not sure if the wiring would hold up if it's mounted on the shielding directly above the hot exhaust.

BTW I was interested in this because I have an aftermarket X-pipe with HFC's which has the secondary O2 bungs much farther down the pipe--why would you want to reposition the bungs behind the secondary cats on the factory exhaust--you thinking of cutting out the primaries or something?
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      02-06-2010, 03:18 PM   #3
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Quote:
Originally Posted by PencilGeek View Post
Yes you can extend them with wiring. My primary O2 sensors have extensions on them.
What kind of wire did you use, and is it soldered in or what?
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      02-06-2010, 04:43 PM   #4
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Quote:
Originally Posted by RedGTS View Post
I asked about that the other day and never got much of a response, but I think the answer is yes, you can splice in a comparable gauge wire and extend them. As far as I can tell no one makes a plug and play extender harness like they do for many GM cars, etc. I'm not sure how you would go about routing the extra wire though. Does the heat shielding in the top of the tunnel area come out so the extra wire could be placed behind it rather than between it and the exhaust? If not I'm not sure if the wiring would hold up if it's mounted on the shielding directly above the hot exhaust.

BTW I was interested in this because I have an aftermarket X-pipe with HFC's which has the secondary O2 bungs much farther down the pipe--why would you want to reposition the bungs behind the secondary cats on the factory exhaust--you thinking of cutting out the primaries or something?
I'm pretty sure the heat shielding comes out since that's how most install the short shifter.

I was thinking if one could extent the post-cat O2 sensors to behind the secondary cats, you could cut out the primary cats or get an X-pipe with HFC's downstream and not get a check engine light. It seems making a longer O2 sensor cable would be easier than trying to come up with some O2 sim- just not sure why the aftermarket folks haven't done this.

.
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      02-16-2010, 11:01 AM   #5
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Quote:
Originally Posted by RedGTS View Post
What kind of wire did you use, and is it soldered in or what?
I'd be interested as well since it would allow cutting out the primary cats, keeping the secondary cats and getting no check engine light. The secondary cats seem to be bigger than the primary ones too.
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      02-24-2010, 03:56 AM   #6
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One more try.
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      02-24-2010, 08:48 AM   #7
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You have to solder the wires. This was pretty common on e46 M3s when installing the European header and mid section.
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      02-24-2010, 11:08 AM   #8
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Make sure to use the correct gauge wires

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      02-24-2010, 11:35 AM   #9
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Ohms need to match
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      02-24-2010, 01:14 PM   #10
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Unfortunately soldering is the only option for now. Anyone seen any aftermarket plugin style extensions?
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      02-24-2010, 01:35 PM   #11
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Quote:
Originally Posted by Kyoshi71 View Post
Ohms need to match
+1

This is a must...

The resistance of the wire extension needs to match the original OE 02 sensor wires, in order to ensure a proper signal feedback from the sensors to the ECU.

The 02 sensors work off very sensitive differential voltage values (to calculate the oxygen content in your exhaust gas stream), so a very high, or very low resistance wire will skew the signal feedback results.

When that happens, the ECU will detect an issue (and throw a fault code)...when there is actually nothing wrong.

A poorly executed solder joint (between the OE O2 sensor wire and the new wire extension) will also be problematic.

You will end up chasing a 'phantom' 02 sensor fault code that doesn't exist.
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      02-24-2010, 01:54 PM   #12
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Thanks guys. I figured it was a little more involved than just splicing wires together.
So it's not possible to male a plug and play type connection?

Also, would you need to move both sensors or just the second, post cat sensor of one were to place it after the secondary cats?
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