Got Service engine soon light went to advance got code p4021 which means warm up catalyst. Only thing i have is a catback exhaust wondering is it the o2 sensor, converter, or manifold ?

 

I've recently got the same code, but I'm stock in the exhaust department...minus a Greddy Evo II canister. It's the primary O2 sensor from what others told me. How many miles on your OZ?

 

107,000 miles going to mitsubishi dealership to get diagnostic on saturday.

 

Could mean the O2 sensor is fried or the stock exhaust manifold (with the catalytic converter) is fried.

 

okay ive been getting the same code on and off
turns on in around 3 weeks if code cleared
but i took a look at the o2 and iunno if its looks bad
but my exhaust manifold looks good!

 

Yeah, that looks about right...but it's just one of those things that "go out" with time. I'm about to do more research about using a cheaper alternative O2...the 1998 Eclipse turbo 2wd O2 sensor (per WADADLIG_OZ [https://www.evolutionm.net/forums/sh....php?t=310888]) is supposed to be a direct replacement. Anyone care to comment on this? Thx

 

but iunno because code went away
and yea i think it is the o2 because im at 105 k and dont think its been changed b4