(1) Open and close the top door several times, then try again.
(2) Power printer off, unplug the main power cable, use knob wrench to remove the back cover of printer. Locate and re-plug plug-J39 (Figure - 1) in lower right corner of main board. Then, power printer and and start a printing test.
(3) Replace top door interlock sensor. (Step of replacement)
(4) Check the cable from top interlock sensor to main board. Replace the cable as needed.
(5) Replace the main board. (Step of replacement)