HomeMitsubishi Fault Codes Mitsubishi Fault Code List 6603 – Bus circuit busy – check if indoor unit, Lossnay unit or anything else has been wired into TB7, instead of TB36607 – Communication issue – no response back from unit whilst system is operational6608 – Communication error – loss of voltage or noise entering the transmission line6700 – control communication error – R22 type unit connected onto M-Net circuit comms error6701 – control communication error – R22 type unit connected onto M-Net circuit comms error6702 – control duplicate address error – two or more R22 type units connected onto M-Net circuit with the same address6750 – control communication error – R22 type unit connected onto M-Net circuit comms error6751 – R/A thermistor fault (P1)6752 – frost protection at I/C (P6)6753 – Comms fault between O/C and I/C6754 – drain fault (P5)6755 – drain fault (P5)6756 – frost protection at I/C (P6)6757 – System error6758 – Comms fault between I/C and O/C6761 – R/A thermistor fault (P1)6762 – TH2 fault check resistance (P2)6763 – Comms fault between I/C and O/C6764 – drain fault (P4)6765 – drain fault (P5)6766 – frost protection at I/C (P6)6767 – comms fault between I/C and O/C6771 – abnormality – high pressure abnormality or low pressure abnormality6772 – abnormality – inner thermostat function, discharge temperature abnormality, shell thermostat function, over current protection6773 – abnormality – radiator plate thermostat function6774 – abnormality – outdoor thermistor abnormality6775 – abnormality – pressure sensor abnormality, indoor/outdoor communication error6776 – abnormality – over current shut-off6777 – abnormality – system error6778 – abnormality – normal6779 – abnormality – refrigerant overcharge, abnormal voltage, abnormal CT sensor6830 – Comms fault between I/C and R/C check connections to MA R/C and check for 12Vdc check R/C not set sub controller6831 – MA R/C communication fault – check connections on TB15 or that the controller was removed while the I/C was powered6832 – MA controller comms fault – check cable length no bigger than 500m, check connection and type of cable used, check R/C not set sub on field settings6833 – MA controller comms fault check cable length no bigger than 500m, check connection and type of cable used, check R/C not set sub on field settings6834 – MA Controller comms fault – check cable length no bigger than 500m, check connection and type of cable used, check R/C not set sub on field settings6840 – A-Control E6/E8 fault – see Mr Slim fault code list6841 – A-Control E7/E9 fault – see Mr Slim fault code list6844 – A-Control EA fault – see Mr Slim fault code list6845 – A-Control Eb fault – see Mr Slim fault code list6846 – A-Control EC fault – see Mr Slim fault code list7100 – Over capacity – (R2 150% index exceeded) (Y 130% index exceeded)7101 – Capacity setting error – SW2 set wrong on indoors, SW5 on YHMA outdoor, (SW3-10 on older kit)7102 – Error in number of connected units – loss of M-Net voltage (short or break), no power to BC, wrong SW5 setting on box, wrong box type7105 – Address setting error – OC or BC addressed wrong7106 – Attribute setting error – SW3-1 setting on a GUF7107 – Port setting error – check if too much capacity on a single port, wiring SW2 setting, wrong SW14 setting or wrong units on a box when using multiple boxes7110 – Check SW5-7 is correctly set7111 – Remote control sensor fault – SW1 – 1 on and no controllers fitted or faulty remote controller7113 – Function setting error – wrong SW5 setting or wrong resistors fitted on YHM-A7117 – Model setting error – SW5 set wrong or wrong resistors in7130 – Incompatible equipment on M-Net – check split with MAC 399 wired onto the TB5 line, not the TB7
