Had to go look at this without knowing a thing about it. Error 1537, pressurizing pump. Book says check for bad connections. Reseated harnesses & checked hoses. Is there something else to check they're not telling me ? Then it says replace pump. Replaced pump & still has error. Found a page in the book that says if the part doesn't work replace main board. do you find this to be true ? I looked up some info, some people said cartridges might be at fault. Checked them for cracks, but I didn't see anything obvious. Wouldn't they be leaky if cracked ? Finally, after checking carts, it would alternately say 'install yellow' when it was installed, or it told me photo black had a cartridge error & to replace it.Tried three different pk with the same message. Board problem? The book tells me not one more letter about it. There are no diagnostic tests, and I can't get into service mode without some kind of error. Guy is waiting for his machine. Anything you could enlighten me with would be greatly appreciated.