TheWyvern

Hello gentlemen,

Recently, I've been getting an intermittent CEL and decided to finally plug in my OBD and get a read on what was going on.

I'm getting code P0139 - O2 circuit slow response (bank 1 sensor 2). I believe this is because I have a straight pipe with a casper O2 ghosting system. However, I'm not exactly sure why this code would come and go, when the system is simply supposed to "fool" the computer into thinking the second O2 is there.

Any insight is appreciated and as usual you guys are the best.

Thanks
-Wyvern

Oats

From what I recall most if not all O2 sensor CEL workarounds don't work on the RX-8.

TheWyvern

Yeah, I've been through a couple of threads like https://www.rx8club.com/series-i-aft...e-97099/page2/, however, I just wanted some insight as to how people have gotten rid of the code, as it's just annoying and I'm not really sure if it's harming anything if I'm honest.

TC4Tay

Only way to get rid of it is with tuning software such as Cobb, MazdaEdit, or Versatune. None the O2 spacer stuff works on these cars. Just take the "ghosting" thing off.

TheWyvern

Considering it at this point, but is the lack of a downstream O2 sensor going to screw with the motor's air/fuel mixture regulation?

My entire reasoning for stripping off the old cat and exhaust was due to the horror stories of failing cats with this car.

TC4Tay

No, second O2 sensor is just there to make sure the cat is working properly. I have a Racing Beat mid-pipe myself for the same reason of the avoiding the cat failure.

TheWyvern

Gotcha. Thanks for the info, I guess I'll just keep resetting the code despite it being annoying.

sk8rg2000

Mine eventually just went away by itself. I was very happy about it.