# O2 Sensor problems.



## G T Oh Damn (Feb 2, 2010)

Ok, for starters I have Pacesetter long tube headers with catless mids on my 05 GTO... up until recently I've had no problems at all with my GTO. I'm not sure if driving in the snow has something to do with it but O2 sensor #1 on bank #1 (sensor before the cat, if there was one, on the driver side) has been replaced three times now... The sensor would be replaced... function 100% properly then.... after a fresh snow storm and after driving in it.... the senor ceases to work. And its only that one sensor, the other three have performed flawlessly. What could possibly be the issue? Spark plugs have only 600 miles on them and the wires are brand new Taylor 10.4mm race wires... not sure where to start looking myself before I have to actually pay someone to find the problem. Any thoughts?


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## Rukee (Feb 8, 2007)

header and collector gaskets 100% sealed up on that side?


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## G T Oh Damn (Feb 2, 2010)

The only gasket is where the actual header meets the cylinder head... and I'm pretty sure that is sealed up nice and tight and all other pipes are clamped together and I know they are all tightened up, just recently checked. But I'll double check there... but if it were moisture or whatever getting into that one side to cause the number one sensor to prematurally fail..... wouldn't sensor two be fried by now as well? No cats so that sensor is only about another foot down the exhaust stream on that side is functioning just fine. Could it be a wiring issue??? I'm usually pretty good at finding problems.... but this one has me lost.


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## jpalamar (Jul 22, 2008)

Exhaust leak can cause you to have bad readings in your front O2s. Def check the collector and gaskets. Make sure your header bolts are still tight and torqued to spec also as I belive you are supposed to re-torque them once you run the car a bit.

I've seen several people have issues mounting the header to the mids correctly. Also you can bottom out and brake where the bolt together.

Also with your Pacesetters, did you use the O2 extentions it came with(the cut and splice ones) or the plug in play ones that you can get from Maryland Speed? If you used the ones that came with the headers, it could just be a lose connection. Either way, unpug and plug in everything just to be safe.


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## MJGTOWISH (Jun 15, 2006)

*Or you could Bypass them... with about 3$ in materials*


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## jpalamar (Jul 22, 2008)

MJGTOWISH said:


> *Or you could Bypass them... with about 3$ in materials*


I don't think you can bypass the front O2s if you want your car to run. Rears you can as they only measure your cat effecienty.


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## MJGTOWISH (Jun 15, 2006)

jpalamar said:


> I don't think you can bypass the front O2s if you want your car to run. Rears you can as they only measure your cat effecienty.


*i'm pretty sure you can on the fronts but i wouldn't do so unless you knew the car was fine. Also I thought we were talking about the rears aka the ones after his ''catless mids''. ?*


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## G T Oh Damn (Feb 2, 2010)

No, defiantly talking about the front O2 sensors... and the rear sensors are tuned out... but they still put off a reading, your computer just ignores them once tunded out. All other sensor are putting off some type of reading while the bank one sensor one puts off barly any. It runs just fine at first.... but then goes to hell once i drive in the snow. I'm gonna go check the header bolts and collect clamps to make sure all is still tight. Oh and I used the O2 wire extenders not the cut up your O2 sensor wire method. I'll put an udate once I check under the hood and under the car. Thanks for all the input.


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## G T Oh Damn (Feb 2, 2010)

Just check the header bolts all tight.... mid pipe clamps.... all tight... so I think that may rule out moisture or water getting on to the sensor... any other thoughts while I got the car in the air?


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## majorforum88 (Mar 31, 2010)

I liked the model loved it...


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## MJGTOWISH (Jun 15, 2006)

G T Oh Damn said:


> No, defiantly talking about the front O2 sensors... and the rear sensors are tuned out... but they still put off a reading, your computer just ignores them once tunded out. All other sensor are putting off some type of reading while the bank one sensor one puts off barly any. It runs just fine at first.... but then goes to hell once i drive in the snow. I'm gonna go check the header bolts and collect clamps to make sure all is still tight. Oh and I used the O2 wire extenders not the cut up your O2 sensor wire method. I'll put an udate once I check under the hood and under the car. Thanks for all the input.


See if you got the o2 connectors switched up, and your o2 senosr might be bad as well

but just to clarify, your upstream senosr's(Before cat) is the one's causing your trouble and not the downstream(after cat) one's right?

FYI, the computer might be saying it's the upstream ones if both senosr are receving the same singal I.e. there both sensing the same but they shouldn't the down stream sensor should read a lower thatn the upstream, but since htere both getting a steady singal(and it thinks it's a cat there) it's gonna throw codes on the front one

Also if your upstream o2's are throwing codes and your sure it's not because of the downstreams, go easy on the car seeing as they control the AFR too.


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## cjtige (Oct 30, 2010)

*o2 sensor delete*

im looking at getting headers and cutting the cats out but dont want to set of cel an have car run bad, is the only way to get around that to get a tune and delete the rear o2 sensors after the cats or what?


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