Brother Printer Error Code 91 — What It Means & How to Fix It

What Does This Error Mean?

Brother error 91 means the printer detects that a cover is open, or the cover sensor is not working correctly. The printer will not print while any cover or door is open — this is a safety feature to protect you from moving parts and hot surfaces inside. In most cases, simply closing all covers fully resolves this error instantly.

Affected Models

Brother HL-L2350DW
Brother HL-L2390DW
Brother MFC-L2710DW
Brother MFC-L2750DW
Brother DCP-L2550DW

Common Causes

The front cover, back cover, or scanner lid is not fully closed and latched
A toner cartridge or drum unit is not fully seated, preventing a cover from closing completely
The cover sensor or latch switch inside the printer is stuck, dirty, or has failed
Debris or a piece of torn paper is caught in the cover's closing mechanism
The cover has been opened and closed too forcefully, bending the latch or misaligning the sensor

How to Fix It

Open and firmly close every cover on the printer — the front cover, the back output tray cover, and the scanner lid if present. Apply gentle but firm pressure until each one clicks shut.

It is easy for a cover to look closed but not be fully latched. Give each cover a deliberate push to make sure it is engaged.
Open the front cover and remove the toner cartridge and drum unit assembly. Check that no paper is caught inside and that nothing is blocking the cover from closing.

Even a small piece of torn paper caught near a hinge can prevent the cover from closing fully enough to engage the sensor.
Reinsert the toner cartridge and drum unit, making sure they slide fully into position. The assembly should go in smoothly and sit flush with the front of the printer.

A drum or toner that is not fully inserted will push against the front cover from inside, preventing it from latching.
Close the front cover with a firm push until you hear it click. Turn the printer off and back on. If error 91 was caused by a cover sensor being temporarily stuck, the power cycle may reset it.

The cover sensor is a small plastic lever or button that the cover presses when it closes. If the sensor is stuck in the 'open' position, a power cycle sometimes frees it.
If the error persists with all covers visibly closed, inspect the cover latch area with a flashlight. Look for a small plastic button or lever near where the cover meets the printer body. Try gently pressing it with a pen tip while the printer is on to test if the sensor responds.

If pressing the sensor manually clears the error but it returns when you release it, the sensor spring is broken or the cover is not pressing it fully. This requires a part replacement.

When to Call a Professional

If error 91 persists after confirming all covers are closed and the toner and drum are seated correctly, the cover sensor or latch switch likely needs replacement. This is a small inexpensive part (typically under $10), but it requires opening the printer to replace it. A repair technician can replace the switch in under 30 minutes.

Frequently Asked Questions

All my covers look closed but error 91 is still showing. What do I do?

When covers appear closed but the error persists, the most common culprit is the drum or toner not being fully seated inside. Remove both the drum and toner cartridge completely, then reinsert them firmly, making sure they slide all the way in before closing the cover. If that does not work, the cover sensor itself is stuck or broken.

Can I print from the back output tray while the front cover is triggering error 91?

No — Brother printers will not print at all when any cover sensor is triggered, regardless of which output path you are using. The cover detection is a safety lockout that stops the entire print mechanism. All covers must be closed and all sensors must be satisfied before printing can resume.

Is error 91 dangerous to ignore?

The error itself is not dangerous — it is a safety mechanism. However, if you somehow bypassed the error and printed with a cover genuinely open, you could be exposed to moving parts and surfaces that reach up to 200°C (392°F) inside the fuser area. Always resolve the cover error before printing.