This is the error code of Brother MFC-9420CN 

Error Code

• 20 - Laser power error
• 21 - Beam detector error
• 22 - Nvram error
• 23 - Engine controller error
• 24 - Process timing clock error
• 25 - Developing motor error
• 26 - Main motor error
• 27 - Scanner motor error
• 28 - Charge HV unit error
• 29 - LVPS error
• 2A - Fuser thermistor error
• 2B - Fuser heater error
• 2C - Fuser temperature low error
• 2D - Fuser temperature low error
• 2E - Fuser temperature high error
• 2F - Fuser ACOFF error
• 30 - Erase LED error
• 31 - Power supply fan error
• 32 - Exit fan error
• 33 - Laser unit fan error
• 34 - Yellow switching clutch error
• 35 - Magenta switching clutch error
• 36 - Cyan switching clutch error
• 37 - Black switching solenoid error
• 38 - Yellow switching solenoid error
• 39 - Magenta switching solenoid error
• 3A - Cyan switching solenoid error
• 3B - Black switching solenoid error
• 3C - Transfer belt error
• 3D - Transfer roller solenoid error
• 3E - Transfer roller solenoid error
• 3F - Fuser unit clutch error
• 40 - Belt marker sensor error
• 41 - HVU connection error
• 42 - Toner empty sensor error
• 43 - Toner empty sensor error
• 44 - Lower feeder unit error
• 81 - Recording paper jam
• 82 - Recording paper jam
• 83 - Recording paper jam
• 84 - Recording paper jam
• 85 - No papertray
• 88 - Recording paper jam
• 8A - The main motor does not rotate
• 8B - The main motor stops suddenly
• A1 - Front cover (scanner unit) front cover
• A2 - Document jam
• A3 - Document jam
• A5 - FAX scanning failure
• A6 - FAX scanning failure. (retry)
• AB - CIS Resolution failure
• AF - CIS positioning error
• B7 - A/D converter reference
• B9 - Light emission intensity error
• BB - White level data error
• BD - Black level data error
• D0 - DF - Modem error
• E6 - Write error in EEPROM
• E8 - Data scanning error
• EA - Document removed at phaseB
• F8 - Battery connection error