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Viessman Boiler Fault Codes and Errors
Just like any other boiler, Viessmann boilers are susceptible to developing issues. And when these issues begin to develop, the boiler will display an error code that will enable you to identify and solve the problem.
This guide covers some of the common Viessman boiler fault codes that you might have found your boiler displaying.
Common Viessmann Boiler Fault Codes and Errors
| Fault
Code |
Description/ Boiler behaviour | Potential Cause | Affected Models |
| 0A | Boiler controls switched to lockout | Faulty fan speed | Vitodens 200 |
| 0B | Blocked burner | A defective flow switch, insufficient water in the system, or wrong flow direction | Vitodens 100-W |
| 0B | Faulty fan speed or the burner controls have switched to lockout | Malfunctioning vent system | Vitodens 200 |
| 0C | Blocked burner | Insufficient power supply | Vitodens 100-W |
| 0C | Burner controls switched to lockout | Flame detected even after the boiler is switched off | Vitodens 200 |
| 0D | Boiler controls switched to lockout | The reset button has been pressed repeatedly | Vitodens 200 |
| 0F | The boiler is in control mode | Boiler requires servicing | Vitrocontrol-S/Vitotronic 100,300-K with MW1 & MW1S |
| 0F | The boiler is in control/ operation mode | Service is required | Vitrotronic 100, 300, 330-K/Vitodens 200-W/Vitocontrol-S |
| 0F | Boiler is in control mode | Vitodens 222-F | |
| 0F | Boiler operation is normal | Boiler service is required | Vitrotronic 200,300 |
| 1A/1B/1F | The burner is blocked | Faulty flow sensor or high flow rate in the boiler | Vitodens 200 |
| 02 | Boiler controls switched to lockout | The boiler safety chain is active | Vitodens 200 |
| 04/05/06/08 | Boiler controls switched to lockout | Faulty fan speed | Vitodens 200 |
| 5A/B7/B8 | Control mode is active | Faulty supply temperature sensor or broken leads, or broken cable sensor | All Viessmann boilers |
| 5C/5D/5E/5F | Control mode is active | Communication fault | Vitotronic 200, 300-K |
| 07/09 | Boiler controls switched to lockout | Incorrect air pressure detected during standby mode | Vitodens 200 |
| 8C/8D/8E/8F | Control mode is active | Communication fault | Vitocontrol-S/ Vitotronic 100,200,300-K |
| 10 | Constant mode active or boiler operation is based on outdoor temperature | Faulty outdoor temperature sensor | Vitodens 200-W, 222-F/Vitronic 300-K, 300,200,200-H/ Vitocontrol-S/Vitodens 100-W, 200-W |
| 10/14/F3/F4 | Burner is in lockout | There is no flame signal | Vitodens 200 |
| 18/D1 | Constant mode or boiler operation is based on outdoor temperature or faulty burner | Faulty outdoor temperature sensor or DIP switch S2 is on | Vitodens 100, 100-W,200-W,222-F/Vitotronic 100, 200, 300,300-K, 050-200-H, MW1 with 100, MW2B with 200 |
| 19 | Boiler operation is based on an outdoor temperature of 0C | Communication error or faulty outdoor temperature sensor | Vitotronci 300 |
| 20 | Insufficient supply temperature | Short-circuit in the temperature sensor | Vitocontrol-S/Vitotronic 100,200, 300-W |
| 20 | Low loss header or temperature sensor in operation while there is no water | Faulty system supply temperature sensor | Vitodens 200-W, 222-F/Vitocrossal 300 |
| 20 | Low supply temperature or the stand-alone control unit has no supply temperature sensor. | Faulty or short-circuited common supply temperature sensor | Vitocontrol-S/Vitotronic 100,200,300,300-K |
| 20 | Low supply temperature or the MW1S sensor is operating without the strap-on sensor. | Faulty or short-circuited strap-on temperature sensor circuit | Vitotronic 100,300-K |
| 20 | The mixing valve is closed | The supply temperature sensor is faulty | Vitotronic 050/200-H,200,200-H,300 |
| 21 | The return temperature sensor is running on its own | The return water temperature sensor has short-circuited | Vitotronic 200,300 |
| 25 | The water in the boiler system is too hot | Low water supply | Vitodens 200 |
| 28 | The mixing valve is closed | The supply temperature sensor has an open circuit | Vitotronic 050/200H |
| 28 | Low loss header or faulty supply temperature sensor | Wiring issues on a supply temperature sensor | Vitrocossal 300/Vitodens 200-W, 222-F |
| 28 | Insufficient flow temperature | Faulty common supply temperature sensor | Vitronic 300,300-K |
| 28 | The mixing valve is closing | Lead break or faulty supply temperature sensor | Vitronic 200,200-H,300 |
| 29/41/49/F80/F81/F83/F88/F89 | The return water temperature sensor is operating on its own | Either circuit 1 or 2 of the return water temperature sensor is open | Vitronic 200,300 |
| 30 | The burner started and stopped during boiler operation | Presence of a short circuit in the water temperature sensor | Vitocontrol-S/Vitocrossal 300/Vitronic 100,200,300/Vitodens 200-W,222-F |
| 30 | The burner is blocked | Faulty or short-circuited water temperature sensor | Vitocontrol-S/Vitronic 100/Vitoden 100-W,200-1 |
| 35 | Boiler activation failure | The reset button was pressed while the boiler was off | Vitodens 200 |
| E38 | Blocked burner | A faulty cable on the water temperature sensor | Vitodens 100-W,200-W,222-F |
| 40/44 | The mixing valve is closing | There is a short-circuit on the temperature sensor | All Viessmann boilers |
| 48/4C | The mixing valve is closing or has closed | The cable connecting the mixing valve supply temperature valve is faulty or has an open circuit. | All Viessmann boilers |
| 50/51/58/59 | There is no DHW heating | The DHW temperature sensor is faulty or is short-circuited | Vitodens 200-W, 222-F |
| 52 | The boiler is in control mode | Faulty or short-circuited supply temperature sensor | Vitotronic 300 |
| 55/56/57 | The boiler is in control mode | The boiler has an internal error or needs maintenance | Vitotronic 300-K,200 |
| 60/68/70/78/BD/BE/BF | The boiler is overheating, or the return control is open | Faulty or short-circuited water temperature sensor or burner control unit | All Viessman boilers |
| 80/81/82/83/FD | The burner control unit is faulty or locked out | Faulty or short-circuited water temperature sensor or burner control unit | All Viessmann boilers |
| 88/89/e6 | The faulty burner control unit | Faulty water control sensor or a lead break | Vitronic 300 |
| 90 to 99/9A/9B/9C/9E/9F/AB | The boiler is in control mode | Faulty or short-circuited temperature sensor | All Viessmann boilers |
| A0/A1/A2/AA/AC | The boiler is cooling down or is operating in emergency mode | Faulty safety equipment or BUS fault | Vitotronic 300,300-K/Vitodens 200 |
| A2 | Fault with the KM-BUS | Vitodens 200 | |
| A3/B0/F1/FE1/FE2 | The boiler burner is blocked | Incorrect positioning of the flue gas temperature sensor | Vitodens 200 |
| A9/B1/BA/BB/BC/FE0 | The boiler is in control mode | Internal communication error between boiler components and the PCB unit | All Viessman boilers |
| B5 | Control mode is active | Faulty internal electronics | All Viessmann boilers |
| B6 | Constant mode is active | Invalid boiler hardware detected | All boiler models |
| B9/ED/F0/FE5/FEC/FED/FEE/FEF/FFD/FFF | Faulty boiler control unit | Internal error | All boiler models |
| D4 | The boiler is cooling down | The fuse F2 has blown | All Viessmann boilers |
| FA/FB | The boiler is in emergency mode or has a faulty burner | The fun is running when it shouldn’t, or a connection hasn’t been plugged in properly | All Viessmann boilers |
| FE4 | Burner is off | Low voltage detected multiple times | Vitocrossal 200 |