Here is a link to the User Guide for your printer.
Found this information which may (stress only may) be the cause of your error message:
This error is usually caused by the Carriage Encoder Strip being dislodged from the sensor mounted on the Print Head/Carriage Assembly. The upper case assembly will need to be opened, and the encoder strip will need to be put back into place. Its also possible that the error can also be caused by grease or fingerprints on the Encoder Strip, even if it is still in place
Here is a link to the service manual for your printer (as well as other similar Brother printers). Scroll to Ch.6-48 for information regarding the CR encoder strip.
If it is all a bit daunting, suggest you either contact Brother service or a professional printer repair service and ask for a quote.