So Im thinking I may put a test pipe in my car for track days....
what does this do to the ecu? if I am not getting readings from the rear O2 sensor how does the ECU deal with this? does it dial back the fuel? Increase it? Do nothing other than throw a CEL?

 

On most OBD II cars, the 2nd HO2 Sensor is merely there to check on the first one - to see if it working. You will likely get a CEL, but it will go awat eventually when you replace the cat, or you can reset it it with a scan tool or via pulling the 7.5a backup fuse.

On my Cobra, I went with a catted x-pipe, but some people were still getting the rear sensor's CEL - so I had my tuner bypass the 2nd sensor - others use MIL-eliminators that mimic the voltages that are normally seen byt he ECU.

 

[QUOTE]Originally posted by Road Rage
On most OBD II cars, the 2nd HO2 Sensor is merely there to check on the first one - to see if it working. You will likely get a CEL, but it will go awat eventually when you replace the cat, or you can reset it it with a scan tool or via pulling the 7.5a backup fuse.

 

Modifry, dont go to Honda to get it, just check Discount or Advance, and if that doesnt work theres another online site that has them for $75 bucks, Ill see if I can find it.