When a Viessmann boiler develops a problem, it may display a fault code on the control panel. The fault codes will include a couple of letters or numbers (or a combination of both) and are designed to help you and your heating engineer to identify and solve any issues. Some of the Viessmann fault codes apply to all Viessmann boilers, whereas others are only relevant to specific models.
If you’ve noticed that a fault code has appeared on your Viessmann boiler and you want to find out what it means, simply refer to the tables below.
Viessmann Boiler Fault Code 5C, 5D, 5E and 5F
Boiler Model
System Behaviour & Diagnosis
VITOTRONIC 300-K WITH VITOTRONIC 200
CONTROL MODE – COMMUNICATION FAULT – VITOTRONIC 100 OF BOILER 5-8
STAND-ALONE CONTROL UNIT WITHOUT SUPPLY TEMPERATURE SENSOR (SUPPLY TEMPERATURE MIGHT NOT BE HIGH ENOUGH) SHORT CIRCUIT – COMMON SUPPLY TEMPERATURE SENSOR
VITOCONTROL-S WITH VITOTRONIC 100 / VITOTRONIC 300-K WITH VITOTRONIC 200
VITOCONTROL-S CONTROLS IN A STAND-ALONE MANNER WITHOUT SUPPLY TEMPERATURE SENSOR (SUPPLY TEMPERATURE MIGHT NOT BE HIGH ENOUGH) COMMON SUPPLY TEMPERATURE SENSOR SHORTED OUT
VITOCROSSAL 300
REGULATES WITHOUT SUPPLY TEMPERATURE SENSOR (LOW-LOSS HEADER) SHORT CIRCUIT – SYSTEM FLOW TEMPERATURE SENSOR
VITODENS 200-W / 222-F
REGULATES WITHOUT SUPPLY TEMPERATURE SENSOR (LOW-LOSS HEADER) SHORT CIRCUIT – SUPPLY SYSTEM TEMPERATURE SENSOR
VITOTRONIC 020/200-H / 200 / 200-H / 300
MIXING VALVE CLOSES OR CLOSED SHORT CIRCUIT – SUPPLY TEMPERATURE SENSOR / MIXING VALVE CIRCUIT M1
VITORONIC 300-K WITH VITOTRONIC 100
VITOTRONIC 300-K, MW1S CONTROLS IN A STAND-ALONE MANNER WITHOUT STRAP-ON SENSOR (SUPPLY TEMPERATURE MIGHT NOT BE HIGH ENOUGH) SHORT CIRCUIT – STRAP-ON TEMPERATURE SENSOR
VITODENS 200-W
REGULATES WITHOUT SUPPLY TEMPERATURE SENSOR (LOW LOSS HEADER) SYSTEM SUPPLY TEMPERATURE SENSOR SHORTED OUT
Viessmann Boiler Fault Code 55, 56 and 57
Boiler Model
System Behaviour & Diagnosis
VITOTRONIC 300-K WITH VITOTRONIC 200
CONTROL MODE MAINTENANCE OR FAULT ON VITOTRONIC 100 OF BOILER 5-8
Viessmann Boiler Fault Code EE and EF
Boiler Model
System Behaviour & Diagnosis
VITODENS 100-W / 200 / 0 / VITOTRONIC 300
BURNER BLOCKED FAULTY AIR PRESSURE SWITCH – AIR DAMPER (FLAP) STUCK
Viessmann Boiler Fault Code FE4
Boiler Model
System Behaviour & Diagnosis
VITOCROSSAL 200
BURNER SHUTS DOWN MULTIPLE DETECTION OF UNDERVOLTAGE
CASE A: BURNER CONTROL UNIT IN A FAULT STATE; SYSTEM COOLS DOWN; BURNER CONTROL LOCKED OUT. CASE B: TYPE OF CODING CARD CASE A: CODING CARD NOT INSERTED IN THE BURNER CONTROL UNIT; FAULTY OR INCORRECT CODING CARD. CASE B: CODING CARD DOES NOT MATCH BURNER CONTROL UNIT
Viessmann Boiler Fault Code 50, 51, 58 and 59
Boiler Model
System Behaviour & Diagnosis
VITODENS 200-W / 222-F
NO DHW HEATING / FAULT WITH DHW SHORT CIRCUIT/OPEN CIRCUIT – DHW TANK TEMPERATURE SENSOR OR LEAD BREAK
Viessmann Boiler Fault Code A9, BA, BB, BC & FE0
Boiler Model
System Behaviour & Diagnosis
VITODENS 200
BOILER COOLS DOWN SENSOR INPUTS ARE NOT READ CORRECTLY
Viessmann Boiler Fault Code F-FA, F-FB and FR
Boiler Model
System Behaviour & Diagnosis
VITOCROSSAL 200 / 400-620 / 186-311
FAN RUNS WITHOUT DEMAND; BURNER CONTROL UNIT IN A FAULT STATE FAN NOT STOPPED; CABLE 100A FAULTY; FAN FAULTY; BURNER CONTROL UNIT FAULTY
Viessmann Boiler Fault Code 8C, 8D, 8E and 8F
Boiler Model
System Behaviour & Diagnosis
VITOTRONIC 300
BURNER CONTROL UNIT IN A FAULT STATE LEAD BREAK, BOILER WATER TEMPERATURE SENSOR, BURNER CONTROL UNIT
Viessmann Boiler Fault Code 52
Boiler Model
System Behaviour & Diagnosis
VITOTRONIC 300
CONTROL MODE SHORT CIRCUIT – SUPPLY TEMPERATURE SENSOR LOW-LOSS HEADER
VITODENS 100-W COMBIPLUS
BURNER BLOCKED (COMBIPLUS ONLY) FLOW SENSOR SHORTED OUT
Viessmann Boiler Fault Code 38
Boiler Model
System Behaviour & Diagnosis
VITODENS 200-W / 222-F / COMBIPLUS
BURNER BLOCKED BOILER WATER TEMPERATURE SENSOR CABLE BROKEN
NORMAL OPERATION WITHOUT INFLUENCE OF RETURN WATER TEMPERATURE OPEN CIRCUIT 1 OR 2 – RETURN WATER TEMPERATURE SENSOR (OF MIXING VALVE CIRCUIT 1)
Viessmann Boiler Fault Code A3, B0, F1, E-E1 and F-E2
Boiler Model
System Behaviour & Diagnosis
VITOCROSSAL 300 / VITODENS 200-W / 222-F / 300
CONTROL MODE (STAYS IN FACTORY DEFAULT SETTING) FAULTY PROGRAMMING UNIT
Viessmann Boiler Fault Code 28
Boiler Model
System Behaviour & Diagnosis
VITOCONTROL-S WITH VITOTRONIC 100
VITOCONTROL-S, VD2/CT3/CM2 CONTROLS IN A STAND-ALONE MANNER W/O SUPPLY TEMPERATURE SENSOR (SUPPLY TEMPERATURE MIGHT NOT BE HIGH ENOUGH) OPEN CIRCUIT – COMMON SUPPLY TEMPERATURE SENSOR
VITOCONTROL-S WITH VITOTRONIC 100 / VITOTRONIC 300-K WITH VITOTRONIC 100
VITOCONTROL-S, WB2B CONTROLS IN A STAND-ALONE MANNER W/O SUPPLY TEMPERATURE SENSOR (SUPPLY TEMPERATURE MIGHT NOT BE HIGH ENOUGH) COMMON SUPPLY TEMPERATURE SENSOR CABLE BROKEN
VITOCROSSAL 300 / VITODENS 200-W / 22-F
REGULATES WITHOUT SUPPLY TEMPERATURE SENSOR (LOW-LOSS HEADER) SYSTEM SUPPLY TEMPERATURE SENSOR CABLE BROKEN
VITOTRONIC 050/200-H
MIXING VALVE CLOSES CABLE BREAK – SUPPLY TEMPERATURE SENSOR
VITOTRONIC 050/200-H
MIXING VALVE IS CLOSED OPEN CIRCUIT – SUPPLY TEMPERATURE SENSOR OF MIXING VALVE CIRCUIT M1
VITOTRONIC 200-H / VITOTRONIC 200 / 300
MIXING VALVE IS BEING CLOSED LEAD BREAK, SUPPLY TEMPERATURE SENSOR, HEATING CIRCUIT WITH MIXING VALVE M1 (HEATING CIRCUIT 1)
VITOTRONIC 300 / 300-K WITH VITOTRONIC 300 / 200
STAND-ALONE CONTROL UNIT WITHOUT SUPPLY TEMPERATURE SENSOR (SUPPLY TEMPERATURE MIGHT NOT BE HIGH ENOUGH) LEAD BREAK, COMMON SUPPLY TEMPERATURE SENSOR
VITOTRONIC 300-K WITH VITOTRONIC 100
VITOTRONIC 300-K, MW1S CONTROLS IN A STAND-ALONE MANNER W/O STRAP-ON SENSOR (SUPPLY TEMPERATURE MIGHT NOT BE HIGH ENOUGH) OPEN CIRCUIT – STRAP-ON TEMPERATURE SENSOR
Viessmann Boiler Fault Code B1
Boiler Model
System Behaviour & Diagnosis
VITOCONTROL-S WITH VITOTRONIC 100 / VITOTRONIC 100 / 200 / 300 / VITOTRONIC 300-K WITH VITOTRONIC 100
EMISSIONS TEST MODE INTERNAL ELECTRONICS FAULT
VITOCONTROL-S WITH VITOTRONIC 100 / VITODENS 200-W
REGULATES AS IF THE OUTSIDE TEMPERATURE IS 32°F (0°C) INTERNAL FAULT
VITOTRONIC 020/200-H
UNDEFINED CONTROL CHARACTERISTICS INTERNAL ELECTRONICS FAULT
BURNER IS STARTED AND STOPPED VIA AN ADJUSTABLE HIGH LIMIT SHORT CIRCUIT – BOILER WATER TEMPERATURE SENSOR
VITOCONTROL-S WITH VITOTRONIC 100 / VITODENS 100-W (COMBIPLUS) / 200-1
BURNER BLOCKED BOILER WATER TEMPERATURE SENSOR SHORTED OUT
Viessmann Boiler Fault Codes – All Viessmann Boilers
Boiler Model
System Behaviour & Diagnosis
B3 and E5
CONSTANT MODE – INVALID HARDWARE RECOGNISED
FA and FB
CONTROL MODE – COMMUNICATION FAULT
A8
CONTROL MODE – COMMUNICATION FAULT – PROGRAMMING UNIT
90, 91, 92, 93, 94, 98, 99, 9A, 9B, 9C, 9E, 9F and AB
CONTROL MODE – SHORT CIRCUIT – TEMPERATURE SENSOR [5] / [6] / [7] / [10]
C9, CA and CB
BOILER DRIVES UP TO ELECTRONIC MAXIMUM LIMIT BOILER DOES NOT LOG IN AT THE CASCADE CONTROL UNIT
5A, B7 and B8
CONTROL MODE – LEAD BREAK, LOW-LOSS HEADER SUPPLY TEMPERATURE SENSOR BURNER BLOCKED / CONTROL MODE – SENSOR CABLE BROKEN
CC and F0
BURNER IN FAULT MODE IONISATION CURRENT TOO HIGH DURING CALIBRATION – BOILER TEMPERATURE LIMITER RESPONDED (F2) – AIR OR BLOCKAGE IN SYSTEM/PUMP FAILURE
B6
CONTROL MODE OPEN CIRCUIT – KM BUS TO SOLAR CONTROL UNIT – EXTENSION AM1 / DE1-DE3 M1 – COMMUNICATION FAULT
D5
BURNER BLOCKED FLUE GAS TEMPERATURE SENSOR NOT PROPERLY POSITIONED / CHECK SENSOR EXTERNAL PUMP FITTED ON THE SYSTEM (100-W) A-3 FAULT
60, 68, 70, 78, BD, BE and BF
NO OUTPUT REDUCTION – RETURN CONTROL OPEN – BOILER WITH MAXIMUM TEMPERATURE SHORT/OPEN CIRCUIT – TEMPERATURE SENSOR [17A]
E2 and E3
BURNER BLOCKED – FAULT: SUPPLY VOLTAGE 24V
40 and 44
MIXING VALVE CLOSES HEATING CIRCUIT 2 WITH MIXING VALVE SUPPLY SHORT CIRCUIT ON TEMPERATURE SENSOR
48 and 4C
MIXING VALVE CLOSES OR CLOSED HEATING CIRCUIT 2 WITH MIXING VALVE SUPPLY TEMPERATURE SENSOR CABLE BROKEN / OPEN CIRCUIT
FC
BURNER IN FAULT MODE GAS VALVE FAULTY OR FAULTY MODULATION VALVE CONTROL / OR VENT SYSTEM BLOCKED. CHECK THE FAN, FAN CABLE AND PCB
FE
BURNER BLOCKED OR IN FAULT MODE STRONG INTERFERENCE (EMC) FIELD NEARBY OR FAULTY MAIN PCB
B2
CONTROL MODE – INTERNAL ELECTRONICS FAULT
B5
CONTROL MODE – EXTERNAL SAFETY EQUIPMENT
80, 81, 82, 83 and FD
BURNER CONTROL UNIT IN A FAULT STATE; SYSTEM COOLS DOWN; BURNER CONTROL UNIT LOCKED OUT SHORT CIRCUIT – BOILER WATER TEMPERATURE SENSOR, BURNER CONTROL UNIT
B4
NORMAL OPERATION / FAULT AROUND BURNER CONTROL UNIT INTERNAL FAULT (PCB)
C2-C8, CD-CF, D2-D8, DA-DF and E0
BOILER COOLS DOWN FIXED HIGH LIMIT HAS RESPONDED OR FUSE F2 HAS BLOWN
F5
GAS PRESSURE SWITCH SHOWS NO GAS PRESSURE / ELECTRICAL CONNECTION FAULT GAS SHUT-OFF VALVE CLOSED; GAS PRESSURE SWITCH FAULTY; MULTIPLE GAS PROBLEMS WITH GAS SUPPLY
F6, 58, F9, F-E1, F-E2 and F-F6
BURNER IN FAULT MODE / EMERGENCY OPERATION FAN NOT AT STANDSTILL / PLUG-IN CONNECTION
