Don't know how much I can help from here and am not a tech either. The codes Hho and P6, however, are listed as codes for future use in the 11_95 edition of 7-62471, the 2100 series Case IH service manual. Have you replaced the header control module itselfIJ If not, do you have one you could borrow that is known to workIJ My dealer would do and has done that for me. Shoot . . . if you were close, I'd even lend you my module for a try.