I am new to this forum. Have not been on any automotive forum in 12+ years so forgive me if this information has been thoroughly covered else where. I drive a 2013 LML LTZ crew cab. 145,000 miles. Second owner. Have owned and driven daily for 3.5 years. Long story short 6 months ago I kept having issues which ultimately resulted in the dealership replacing the entire DPF tank, fluid heater, etc. as the truck had went into limp mode. I should have deleted it then. As of 4 days ago I got a CEL and a message on my display stating “cleaning exhaust filter keep driving until message cleared”. I have read that you must drive and drive somewhere in order for the exhaust filter to clean itself but the specifics of how for, how long, and the perameters have been argued/disputed. The code is P0420 and my reader says “Catalyst System Efficiency Below Threshold (Bank 1)”. So is it the cat or the exhaust filter? Can somebody please offer their best opinion and input on this matter. I am more than eager to delete everything, but still trying to finish paying for another priority at this time.