CEL P1165, I'm stumped

Crono139

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F23A4
Neuspeed N2 header
Random Tech cat (w/ non-fouler trick)
Tanabe exhaust

The header and cat were installed at the same time and I ended up with a CEL for the secondary O2 sensor (not sure on the exact code as I used the paper clip trick). Two spark plug non-foulers were used to clear this CEL.

After a reset, another CEL came up, this time for the primary O2 sensor. I now have a scan tool so I know that the exact code is P1165 (Primary heated O2 sensor circuit range malfunction). I swapped out the current O2 sensor with a Denso, no luck. I swapped out the Denso for a Honda one this past weekend, also no luck. I've been clearing the codes with the scan tool, not by pulling the battery but I don't think that it matters.

It has to be the header that is causing the problems but I'd rather not swap it out. The only other possible solution that I can come up with is to try the non-fouler trick on the primary O2 sensor. I don't think anyone has done this before, though.

Any other suggestions? Thanks in advance.
 

001Stunna

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F23A4
Neuspeed N2 header
Random Tech cat (w/ non-fouler trick)
Tanabe exhaust

The header and cat were installed at the same time and I ended up with a CEL for the secondary O2 sensor (not sure on the exact code as I used the paper clip trick). Two spark plug non-foulers were used to clear this CEL.

After a reset, another CEL came up, this time for the primary O2 sensor. I now have a scan tool so I know that the exact code is P1165 (Primary heated O2 sensor circuit range malfunction). I swapped out the current O2 sensor with a Denso, no luck. I swapped out the Denso for a Honda one this past weekend, also no luck. I've been clearing the codes with the scan tool, not by pulling the battery but I don't think that it matters.

It has to be the header that is causing the problems but I'd rather not swap it out. The only other possible solution that I can come up with is to try the non-fouler trick on the primary O2 sensor. I don't think anyone has done this before, though.

Any other suggestions? Thanks in advance.

DO NOT put a spacer on your front o2. Messing with the readings of your front o2 is not what you want to do as that's what decides on your a/f ratio.

If you've already changed the o2 with a new one i'd check on the wiring. Check for poor connections or loose wires at under the under-hood fuse/relay box, primary HO2S relay, and the ECU.

Is your o2 sensor plugged into the collector of all four ports or plugged into one port only? Was any kind of wiring extension used?
 

Crono139

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Is your o2 sensor plugged into the collector of all four ports or plugged into one port only? Was any kind of wiring extension used?

The O2 bung is located where the middle runners meet (not the best pic but you get the idea):
IMG_1375A.sized.jpg


Nope, no wiring extension.
 

001Stunna

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The O2 bung is located where the middle runners meet (not the best pic but you get the idea):
IMG_1375A.sized.jpg


Nope, no wiring extension.

That pic shows the o2 bung only on the 3rd port...meaning your a/f is only being based on how cyl#3 is running only. Not the collective of all four cylinders. They all meet well down below. Also you are buying the o2 sensor for the f23a4 engine right? no the f23a1? The A1 uses a narrow-band O2 sensor (like most other cars) and the ULEV A4 uses a wide-band sensor coupled with a 32-bit engine computer to keep emissions to a minimum.

In addition have a look at this TSB which might apply to you regarding an OEM o2 sensor part# upgrade.
http://www.justanswer.com/uploads/acuramstr/2008-09-17_210125_p1164.pdf

It seems you need to have
Denso# 234-9025 (upstream)
or
OEM# 36531-PAA-307 (upstream)
or
NGK# 24809(upstream)
 
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619rcr

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circuit range malfunction, sounds like an open wire. disconnect your ecu & check all the wires down to the o2 sensor. You might have broke a pin off the wire or ripped a wire chging your header or something else. Theres only 4 wires for the o2 sensor. should take a few minutes.
 

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