I got a CEL light about a month or so ago. I have an OBD2 Scanner and it read a P0420 code. Catalyst System Efficiency Below Threshold. I reset the ECU and all was good for about 1600 miles. Then all of a sudden my CEL light came on again today. P0420 Code again. I am running a custom Invidia midpipe for my AWD and invidia axelback. Also have HPS intake pipe with F sport filter. Would it just be an exhaust leak or bad catalytic converter or something else?

I am thinking, I should have my stock midpipe/axelback put back because I am still under warranty and take it to Lexus. The only issue is that I had a muffler delete done before I bought my axelback. So I guess I can have them weld the mufflers back on, but would Lexus notice that it was welded on and say due to that it voids my exhaust warranty?

Any advice would help, thanks.

 

Do you have Cold air intake or aftermarket exhaust ?

 

Got the same code with an ARK Exhaust!
Bump

 

I had the same problem. The issue is the gaskets that invidia provided for the midpipe are crap and wears out so there is a leak from the cat. Change that out to OEM gaskets and you should be good.

 

Going to order the gaskets as i think i didn't keep them when i put on the invidia parts. I hope the gaskets are the solution, would be a PIA to have to put on my stock parts and then swap em out again

 

and today the CEL randomly went away...

 

yep, your exhaust is definitely leaking. leaking exhausts will throw codes every now and then. replace gaskets and you should be good