I have a HP Officejet G4500-g10gn multifunction printer. It works OK on printing b/w, color from computer; scan to pdf. However, when I want to do b/w copying, it prints out a blank page; color copying, it only prints only color part but not the black text. I checked that ink black cartridge level is OK and the scanning lamp lights on and moving.

Please advise me how to diagnosis and fix this problem. Thanks.