I am hoping you guys can help me. I have a 2016 F150, 3.5 Ecoboost with 125,000 miles and have been chasing the P0430 and P0420 codes, catalyst system efficiency below threshold bank 1 and 2, for some time now. At first, the CEL was intermittent, now it has been constantly on. Several months ago, I also had a misfire code which I fixed (cracked plug, replaced all 6). I don’t have drivability issues, however, I recently noticed a drop in fuel efficiency of about 2 mpg. I had my truck into a muffler shop to replace the flex pipe and mentioned the codes. The shop told me that there’s nothing wrong with my cats and to just keep clearing the codes. I tried cataclean which cleared the code for a few days but it came back.

I have 125,000 miles and have not replaced the O2 sensors yet. From my research, bad O2 sensors could be the cause of the codes.

My truck has a history of exhaust leaks with having the left exhaust manifold replaced twice and the right manifold replaced once.

Any advice would be greatly appreciated!

 

Did you ever resolve this issue? Having similar issues with a '15 ecoboost. Thanks