Hi Kenny.
what scanner do you have?
a generic ‘cheap scanner’ will not pick up every code I have found in my experience.
a garages equipment is much more advanced.
my mates mini failed in emissions badly and was told the whole cat, exhaust and sensors needed replacing… a full tank of premium fuel and a couple of bottles of redex, followed by an hours run before the MOT sorted everything 😀
how handy are you with spanners? I wouldn’t have thought it would be that difficult to replace.