An E5 most frequently comes from the door connector . When you open the right side on the upper left there is a black connector. Those contacts may be dirty or bent. Carefully clean and reform if necessary. I will send you some other info to follow.
Also if you take the copy cartridge out and and clean all the contacts inside the machine you can see, it may also correct it.
Recurring problem with
E5. Door connector has been replaced, contacts on Interconnect board are clean and shiny, but interlock connection still not reliable. When you remove the rear motor cover and press on the door connector, the
E5 goes away and the fuser starts to warm up.
The door connector is mounted loosely to the door to allow it to locate itself with the interconnect board when the door is closed. If it is too loose, the connector will not make good enough contact to complete the interlock circuit