P0483 Code on 2004 Forestor.. Fan control....What should I check first?

Hot wire the fans and see if they are capable of working. You may be able to see if the fans can work by turning on your air conditioning. If the fans work than you will need to locate and check the radiator fan sensor. Also check your fuse panel to see if the fan circuit is fused. Relays generally last fairly well but it never hurts to check them. By the way, its possible to jump the fans at the relay harness or box connection if accessible.