The car is a 00 civic si. Has intake, K&N filter, copper exhaust manifold gasket, 4-1 JDM DC header, SMSP 2.5 cat, 2.5 exhaust pipe and muffler. A year ago I decided to put the header back on after about 2 years with out it. Soon after I put it on I get a CEL (P0133 Rear Air/Fuel Ratio (A/F) Sensor (Bank 1, Sensor 1) Circuit Slow Response) After reading about the CEL I canged the front O2.

I also got another ECU just to make sure it wasn't the ECU. IT ran fine for about a month and a half and now I get the CEL again.

Anyone have any ideas what the problem is?? Can O2 sensors go bad so quick?? I bought of this board from a member and he said it was new. Seemed to me when it got here to be new, it was for an integra though.

 

Anyone??