you will think this is the dumbest solution ever.
the atc light will light up if you have a dirty fuel filter.
my light came on right after I first bought it and the dealer said they changed the oil and fuel filters, after posting the same question on here someone told me to check out my fuel filters...(I didn't believe them)
so I called Monaco (they were correct ) so I crawled under to find out the dealer had missed one fuel filter, I changed it and light has stayed off
Good luck