My CEL, just came on I checked it with the interceptor, says P0420: Cat Converter Efficency, I just switched over to 91 octane from 87.. not sure if that will have anything to do with it.

Also, ive had a problem with the second sensor before bare wire grounding out. Fixed that.

Got new pacesetter header, hi-flow cat, full exhaust and have not had a problem for about.. 2-3 months I belive.. Any ideas?

I guess my 02 sensors could be going.. just wanted to make sure it was not a 87 t 91 problem..

Going to try to clear it with the interceptor and see if it comes back... any help would be appreciated.

 

i had the same prob it's your high flow cat here's a link a member from here gave me and this fixed my prob
Here ya go, this should do the trick

http://cgi.ebay.com/ebaymotors/O2-SE...Q5fAccessories


This is for the O2 sensor after the cat (or after where it should be)... the other one sets your A/F, and you don't want to run lean.

 

link is broke

 

here try this one
http://cgi.ebay.com/ebaymotors/O2-SE...4506.m20.l1116