P0420 CEL light fix


New Member
After much reading and asking around I think I have found a cure for the P0420 CEL that the CJ CY CF lancer will give you after a high flow catalytic converter is installed.
The error won't show up straight away , took quite a few hundred kilometres to show up.
Im pretty confident I have got it sorted by buying a mini cat adaptor from eBay.
I have put all the info together here

Hope this helps someone else



Forum Administrator
From memory this only briefly worked for me but then the CEL came back.

I had stock cat with RRM headers (which had to have a new flex joint installed locally as their *poo* one failed)....


New Member
Been one week now. Done a few hundred kilometres since I dropped the mini cat onboard.
Zero issues since installed.
I think we have a winner.
No excuses for not running a full system on the lancer now.