After having my Kooks headers and catted Y installed I threw a code 420
Cat system 1 Bank 1 efficiency below threshold. I am thinking this is due to running rich? I do not think the new cat is bad. I probably need a tune? What do you guys think. Thanks

 

this happens on occassion with high flow cats not located in the stock position...you'll probably end up needing sims or to turn the code off.

 

I thought sims were only needed if no cats are run. If car is running rich I think leaning it out will help. Anyone else have ideas

 

It's the same code folks get when they gut their stock cats,like me.I had to get rear o2 sims.The air is flowing thru the cat to fast.The PCM thinks the cat is bad.It richened my car also.Now i have Longtubes,front o2s ok,rears still have sims and no cats..

 

Aftermarket high flow metallic cats will often set a 420 code. Just turn it off. Everything's fine.

EC

 

oh common... am I the only one that found the title of this thread humorous? =p

 

haha been doing to much of this have you?

 

I set the same code after my dynatech and cat install. Change the code to no error reported and you should be fine.