SC codes

Way down in Belize, Central America, we have being experiencing problems with our Linoprint C751 which is a Heidelberg labelled Ricoh C751 engine. we have gotten a SC 236 code and have used the manual and followed the process of checking the wiring harness, changed the IPU Board and have even changed the YM Laser but have seen no change. Upon turning on the unit the Self Check remains and we need to open a door to bypass so that we can send a print but the SC code keeps returning... Please Help!!!