O2 sensors front rear, diffrent? - 986 Forum - The Community for Porsche Boxster & Cayman Owners

mn box s · 04-08-2007, 08:24 AM

I just replaced my exhaust full system with fabspeed test pipes. I was getting cel for 2nd bank o2 and maf so I replaced the MAF and ordered 4 new o2s I have headers now and the front o2 wouldnt reach so I used the rears and they pluged in. Fabspeed claims no cel. I have not had time to scan again and wondering if people have the same problem. Also hunting for idel badly 90% of the time. I now have only 2 o2s hooked up? CEL went off after install but came on with in a minute again.

mikefocke · 04-08-2007, 10:24 AM

I hope you are not buying OEM ones.

Sources and Part Numbers

tholyoak · 04-08-2007, 01:42 PM

It sounds as though you are running no cats, replacing both the front cats with headers and the rears with the test pipes. If this is the case you will have issues. The DME needs to see a drop between the front and rear O2 sensors to know the cats are working, if it does not, CEL.

Todd

mn box s · 04-08-2007, 02:02 PM

What is the way around this? Can GIAC chip be programmed for this set-up? Why does fabspeed claim no CEL? Car runs strong even if in a limp mode. Any help appritiated.

tholyoak · 04-08-2007, 02:09 PM

I believe Fabspeed claims no CEL when you use their test pipes alone. You would still have the main cats on the headers which would result in no problems. In order to run no cats, you would need to flash the DME with a new program, either custom or ROW.

Todd

mn box s · 04-08-2007, 02:26 PM

Thanks for the help I'll try that. Do you think dummy o2s for corvette or mustang would help? Or weld in bungs on the test pipe. Thats what I did for my Civic Si race car. (10k rpm 11.5:1 1.6L vtec NA 206whp 2300LBS) no cats.

z281974 · 04-08-2007, 03:29 PM

My understanding is that the DME is looking for a specific output from the rear O2 sensors. Therefore you can't (1) eliminate them, nor (2) install them further back in the exhaust without a working catalytic converter in between. Re-programming the DME should resolve the CEL problem. A less expensive solution which might work (??) is the use of O2 simulators in place of the rear O2 sensors. The site www.o2sensorsimulator.com provides an example of what's available for a relatively small amount of money and may be worth a try. Read the info at this site and decide for yourself.

Tom