How to fix Canon IR2520 Cover sensor error?

SOURCE: Error: "Back cover is open. Close back cover."

We had this problem. It turned out there was actually a piece of paper stuck in the printer! It wasn't so easy to see it from the rear.

We removed the paper from the front by taking out the ink cartridge first. Turned the printer back on and everything was fine.

SOURCE: close front cover

THERE IS A PROBLEM WITH ONE OF THE COVER SWITCHES. EVERY COVER HAS A SWITCH, ONE OF THEM MAYBE STUCK, BROKEN, OR MISSING. GOOD LUCK.

SOURCE: Brother DCP-7020

Props to Profjake. I followed his advice and problem solved! Here is what I found out.

I had the "Back door open" error on the LCD panel. There is a "interupter" type of sensor that detects if the back door is open or closed. When the back door is closed a lever is pushed forward and blocks the interupt module. The lever that blocks the sensor was not reqching the sensor horizontally - it was too far to the left. The lever on the far right is part of a 6" rod that goes across the middle of the paper path. The rod had jumped out of it's "home" position to the left and it was bowed a little bit. I carefully re-seated the rod to by gently lifting it and moving it to the right into a slot 1/8" from where I found it. The error cleared immediately. The was most likely caused by removing a paper jam.

Once again props to Profjake as his advice led me to the solution.

Hu said that!

SOURCE: close top cover error on laserjet p3005

http://www.feedroller.com/Store/Service%20Manual/HP%20LaserJet%20P3005%20Parts,%20Service%20Manual.pdf

Hi, this is a link to the service manual for this printer

SOURCE: Brother DCP 7020 error 'back cover open close

• Open the back cover.
• Pull the flap down that hides the orange roller on the fuser (be careful: it's hot)
• Locate the inner flap that runs from the centre to the right hand side.
• 3/4 along the right hand side, there is a tiny little perpendicular appendage on this bar that should sit in a slot. Locate it properly and the error will go away. You can go that by slightly bending the slot if fits into on the inner flap. The appendage can get jossled out of the slot when one is removing jambed paper.