The printer is showing error 51 and not printing

Control Panel message
51 PRINTER ERROR
Description
Beam error
Action Laser scanner cable connectors are faulty or laser scanner assembly is defective Most likly it is the laser/scanner assembly. The motor is probably not spinning at the right speed. You would need to find an old hp 4 no longer working and switch the laser/scanner. It is the "black box" located under the top cover. You would need to remove the right side cover, the top cover, the left side cover and the output assembly. Remove all the cables from the scanner retaining clips. Remove the three cables plugged into the scanner and remove the four screws attaching the scanner to the frame. When replacing the scanner make sure the shutter control arm on the left front side of the scanner is attached correctly so that the shutter closes when the toner cartiridge is removed. You could first try to remove the 3 connnectors and reset them.