suggest you read the comments at bottom as some had to adjust a couple of the instructions. Here is another link but it focuses on the error 46 the purge counter

The manual on page 70 says to: Disconnect the machine from the power for several minutes, then reconnect it.

Found this on fixya.com it relates to Print error 50, but use at your own risk!

Hi, I had this same problem and it is an easy fix. It is similar on all brother printers but mine was a 5860CN.

Lift the lid on your printer and at the back you can see the opening where the print head is. With the power off, use your finger to move the print head into the middle. Now feel under the lip of the cover at the front of the gap and you will find a plastic strip that runs from one side to the other. This is the encoding strip and it what the print head uses to read where it is. This encoding strip is easily pushed out of position when a paper jam occurs and all you need to do is to get it back into position. Using both hands use a finger on either side of the print head and lift the encoding strip upwards slightly and move slightly towards the back of the printer. This will locate it back into the correct position in the print head when you release. You can feel this with your fingers. Power back on and the problems will be gone! Remember and be gentle so as not to damage the encoder strip!

when you checked for paper jammed, did you also check the print head was in the centre and not jammed at the left side? Here's how to move it back to centre solutions.brother.com

Try this way to start it off, Switch on the machine while holding down the "Menu" button, until all the leds are flashing on/off and it should enter the "maintenance" mode, then it's the usual:

• Press 80
• Press the "Mono start" button several times until you see "purge: xxxx"
• Press "2783" in order to reset the purge counter. You will see: "purge:0000"
• Press the "Stop" button.
• Press "99" to exit the maintenance mode.