Well I am depressed...... I thought I checked this out thoroughly and to a person that had I asked that used these bypass pipes no one had problems with the O2 sensor on the Cats.

The removal of the mufflers was truly easy as many professed. I took the car for a test drive sounded great ~ 5 miles into the test ride the Check Engine light comes on. I just guessing here but I am willing to bet that it is the O2 sensor that took a hit. If it is the O2 sensor I assume this will rob the car of performance but my question can I damage the engine? I will need to get it into a shop to have this checked out and fixed just need to know how soon I need to get there?

Anyone have problems with an O2 sensor?

 

muffler bypass pipes on GT3 for a year...actually been on and off the car twice for Laguna Seca...no cat issues or check engine lights (5k miles)...mine is a MkII 2005...if the check engine light stays on it is safe to drive (have error code checked) if the cel is flashing you are not to drive...

 

I had it happen after a track weekend with the pipes, by the time I took it to the dealer I had remounted my mufflers, so all was covered.(cats are 1465$ each plus labor)
The CEL light in a 996 is always emissions system related, so it's ok to drive. The car automatically goes into limp mode with a CEL by design. Just put your mufflers back on before going to the dealer.

 

I got a PM but I deleted it so I'll thank that individual now, THANK YOU! I was told to hook everything back up stock again and disconnect the battery for ~ 1 minute. This re-sets the computer taking out any blips but real problems will show up again. So it worked I am very happy to say and the car is staying stock for now on the exhaust side for awhile.

Anyone interested in Fabspeed muffler by-pass? Used slightly...

 

I dont get it, why do some people have the bypass w/o any problems & some people blow their cats?

 

how much do you want for the bypass pipes??

Do any companies make O2 sims?

Are the GT3 O2 sensors more "lenient"?

-Keith

 

isnt the issue not only that the 02 sensor malfunctions, but also that the cats will break down inside, meaning you will need to replace the cats too?

 

the only possible reason I have come up with yet is this...perhaps the mufflers isolate the cats and O2 sensors from moisture that the bypass pipes allow to reach the cats..I haven't had any problems but I don't take my car out in the wet either and I live in a pretty dry climate....just a thought...

 

I did a lot of research both on here and Renlist and found nothing that suggested that the CATs could be damaged or the O2 sensor failure was a problem. Many users said they had used them mostly for track days others as there daily driver for well over a year with no problems.

I think the only way the CATs would break down inside would be if you allowed water to enter in or you continued to drive the car with the CEL on. From what I have heard an O2 sensor gone bad will cause the air/fuel mixture to be wrong leaning out the car and overheating the CATs causing the damage.

 

Actually my CATs are fine and so is the 02 sensor for some reason with the bypass pipes on it tripped the sensor causing a CEL, I just don't think it's worth the risk after my close call.

 

You could be right I noticed moisture in the bypass pipes when I removed them to re-install the OEM mufflers. I live in San Jose, CA not really a dry environment ~30% humidity.

 

I was gonna do that, but changed my mind, so just bought the Evoms exhaust instead

 

I got tired of having to pay to get a CEL light checked out so I got a tool that will read the OBD-II codes and also reset the light. Mine is the AutoEnginuity ScanTool but there are many out there on the market. The bottom line on your issue would be to read the actually warning code(s) to identify the exact problem. I don't doubt it is emissions/fuel-air ratio related but until you read the code you cant know for sure whether it is something that will destroy your CATs or not.

 

When mine went, it was the Monday after a track weekend, I had replaced the mufflers Sunday night. As soon as it went on I stopped by the stealer and they cleared it, within 20miles it went on again(CEL), then replaced cats under warranty.
Somehow there is a definite relationship btwn bypass pipes/track/CEL's/cat failure.

 

The O2 sensor may have been tripped by accidentally touching the tip with a greasy hand during installation. This is commonly the case. Once the grease burns off and the code is cleared the problem seems to go away. Another common problem is that the computer has not properly programed itself for the new exhaust flow. Therefore by jumping on it immediately after installing them could trip an O2 sensor. In some cases it takes a couple times of clearing the code and then you never see it again.