Viessmann Fault Codes

Select a fault code to see its meaning, common causes and how to fix it.

10 Fault code 10 on Viessmann boilers signals that the boiler's control system has detected a short circuit in the outdoor… Read more →
18 Fault code 18 on a Viessmann boiler signals that the boiler has detected a break or open circuit in the outdoor… Read more →
19 Fault code 19 on Viessmann boilers indicates that the burner control unit has detected a problem with the fan —… Read more →
1A Fault code 1A on a Viessmann boiler indicates that the boiler's control board has detected the fan is still spinning —… Read more →
1b Fault code 1b on Viessmann boilers indicates that the burner control unit has gone into lockout because the fan has… Read more →
1F The F1 fault code on Viessmann boilers — sometimes displayed as '1F' depending on the control panel orientation or… Read more →
20 Fault code 20 on a Viessmann boiler is a fan and burner control fault that causes the boiler to enter a lockout or… Read more →
28 Fault code 28 on Viessmann boilers signals that the boiler has shut itself down because its fixed high-limit thermostat… Read more →
30 Fault code 30 on Viessmann boilers signals that the burner control unit has entered a safety lockout because the fan… Read more →
38 Fault code 38 on Viessmann boilers indicates that the boiler's control system has detected the fan has not come to a… Read more →
40 Fault code 40 on a Viessmann boiler indicates that the burner control unit has triggered a safety lockout because the… Read more →
44 The F4 fault code — sometimes displayed as '44' on certain Viessmann boiler panels — means the boiler's control board… Read more →
48 Fault code 48 on a Viessmann boiler — most commonly seen on the Vitodens 200 — indicates that the boiler has been… Read more →
4C The 4C fault code (grouped by Viessmann alongside code 48) indicates that the boiler's control system has detected a… Read more →
50 Fault code 50 on Viessmann boilers — most commonly seen on the Vitodens 200-W and 222-F — signals that domestic hot… Read more →
58 Fault code 58 on a Viessmann boiler indicates that the control unit has detected an open-circuit or complete loss of… Read more →
90 Fault code 90 on a Viessmann boiler signals that the burner control unit has entered a lockout or emergency mode… Read more →
91 Fault code 91 on Viessmann boilers signals that the burner control unit has detected the fan is still spinning (or… Read more →
92 Fault code 92 on Viessmann boilers signals that the burner control unit has detected the fan is still rotating when it… Read more →
93 Fault code 93 tells you that the boiler's burner control unit has triggered a protective lockout because it detected… Read more →
94 Fault code 94 on Viessmann boilers signals that the solar control module has detected a short circuit on the domestic… Read more →
98 Fault code 98 on a Viessmann boiler (most commonly the Vitodens 200-W) indicates that the control system has lost a… Read more →
99 Fault code 99 on Viessmann boilers signals that the burner has gone into a safety lockout because the fan has not come… Read more →
9A Fault code 9A on a Viessmann boiler indicates that the burner control unit has detected the fan is still spinning — or… Read more →
9b Fault code 9B on a Viessmann boiler signals that the control system has detected an open circuit on the hot water… Read more →
9C The 9C fault code appears on Viessmann boilers fitted with a Vitosolic solar control module and indicates that the… Read more →
9E The 9E fault code appears on Viessmann boilers equipped with a solar thermal circuit and indicates one of three… Read more →
9F The 9F code appears on Viessmann boilers equipped with an integrated solar thermal system — most commonly the Vitodens… Read more →
A3 The A3 fault code appears across several Viessmann boiler ranges but can carry two distinct meanings depending on your… Read more →
A4 The A4 fault code on a Viessmann boiler signals that the boiler has detected a problem related to its return water… Read more →
A7 The A7 code appears when the boiler's control board detects that the fan has not reached a complete standstill at a… Read more →
b0 The B0 fault code on a Viessmann boiler indicates a burner blockage triggered by a short circuit at the flue gas… Read more →
b1 The B1 fault code on Viessmann boilers points to a problem with the boiler's coding card — a small but essential… Read more →
b5 The B5 fault code on a Viessmann boiler signals that the main control unit has detected an internal error it cannot… Read more →
b7 The B7 fault code on Viessmann boilers indicates that the burner has been blocked — meaning the boiler will not fire —… Read more →
b8 The B8 code on Viessmann boilers signals a 'Burner Blocked' condition, most commonly caused by a fault with the flue… Read more →
bA The bA fault code appears on Viessmann boilers when the burner has entered a locked-out error state because the fan was… Read more →
bb The BB fault code on Viessmann boilers indicates that the burner has entered a fault or lockout state because the fan… Read more →
bC The bC fault code on Viessmann boilers indicates that the boiler's control board has detected an issue with the fan at… Read more →
bd The BD fault code on a Viessmann boiler indicates that the burner has been locked out because the boiler's control… Read more →
bE The bE fault code appears on Viessmann boiler displays when the boiler's control board detects that the fan has not… Read more →
bF The bF fault code on Viessmann boilers indicates that the boiler's control unit has detected the fan was not at a… Read more →
C1 The C1 fault code on Viessmann boilers signals that the burner control unit has gone into lockout because the fan… Read more →
C2 The C2 code on a Viessmann boiler signals one of two problems depending on your model. On most Viessmann boilers it… Read more →
C3 The C3 fault code on Viessmann boilers indicates a problem with the outdoor temperature sensor used for weather… Read more →
C4 The C4 code on Viessmann boilers points to one of two underlying issues depending on your specific model. On Vitodens… Read more →
C5 The C5 fault code on Viessmann boilers indicates that the boiler has entered a degraded 'control mode' because it has… Read more →
Cd The Cd fault code on Viessmann boilers indicates a problem with the outdoor temperature sensor, also known as the… Read more →
CF The CF code indicates that the boiler's control system has detected a problem with the outdoor weather compensation… Read more →
D4 The D4 code appears on Viessmann boilers when the burner control unit detects that the combustion fan has not come to a… Read more →
d6 The D6 fault code on Viessmann Vitodens boilers indicates that the burner control unit has detected a problem with the… Read more →
d7 The D7 code indicates that the boiler's control system has detected a fault on the DE2 digital input of the EA1… Read more →
d8 The D8 code places your Viessmann boiler into control mode after its control unit detects a fault signal arriving… Read more →
dA The dA fault code indicates that your Viessmann boiler has detected a short circuit within the thermistor (temperature… Read more →
db Fault code db on a Viessmann boiler indicates that the control unit has detected a short circuit in the room… Read more →
dC The dC fault code on a Viessmann boiler indicates that the control unit has detected a short-circuit in the room… Read more →
dd The dd fault code appears on Viessmann boilers with older Vitotronic controllers and signals that the boiler attempted… Read more →
dE The dE fault code appears on Viessmann boilers when the control board detects that the fan has not come to a complete… Read more →
dF The dF code on a Viessmann boiler indicates that the burner control has entered lockout because the fan has not come to… Read more →
E0 The E0 code on a Viessmann boiler points to a problem with the LON (Local Operating Network) — a proprietary… Read more →
E3 The E3 fault code on Viessmann boilers signals that the burner has entered a fault or lockout state, but the precise… Read more →
E4 The Viessmann F4 fault code — sometimes searched for as E4, which is how certain older Vitodens displays render it —… Read more →
E5 The E5 fault code on Viessmann boilers has two distinct meanings depending on your specific model. On the Vitodens 200,… Read more →
EA The EA fault code indicates that your Viessmann boiler has attempted to light its burner on multiple occasions and… Read more →
EB The EB fault code on a Viessmann boiler indicates that the boiler failed to detect a valid flame signal during its… Read more →
EC The EC fault code appears on older Viessmann boiler models and signals a circulation-related burner lockout. In plain… Read more →
Ed The Ed fault code on Viessmann boilers indicates that the burner has entered lockout (fault mode) because the control… Read more →
EE The EE fault code on Viessmann boilers has two related interpretations that can overlap depending on your specific… Read more →
EF The EF fault code on Viessmann boilers signals that the boiler has entered a protective shutdown state because either… Read more →
F0 The F0 fault code on most Viessmann Vitodens boilers (including the popular 100-W and 050-W) indicates that the boiler… Read more →
F1 The F1 fault code on a Viessmann boiler indicates that the flue gas temperature sensor has detected temperatures beyond… Read more →
F2 The F2 code on a Viessmann boiler signals a burner lockout — the boiler's built-in safety system has detected a problem… Read more →
F3 The F3 fault code on Viessmann boilers points to a problem with flame establishment or flame detection during burner… Read more →
F4 The F4 fault code on a Viessmann boiler means the control system has been unable to confirm that the burner lit… Read more →
F5 The F5 code appears on Viessmann boilers when the PCB cannot confirm that the air pressure switch is functioning… Read more →
F6 The F6 fault code on a Viessmann boiler indicates that the boiler water temperature sensor is producing a reading that… Read more →
F8 The F8 fault code on a Viessmann boiler means the burner control has entered lockout because the fan was still spinning… Read more →
F9 The F9 code on a Viessmann boiler indicates a fan or blower fault that has triggered a safety lockout. The boiler's fan… Read more →
FC The FC fault code on a Viessmann boiler signals that the burner has been forced into fault mode — typically because the… Read more →
FD The FD fault code on a Viessmann boiler means the boiler attempted to light but failed to detect a stable flame — or… Read more →
FE The FE code on a Viessmann boiler indicates a fault linked to the printed circuit board (PCB) or a problem with the fan… Read more →
FF The FF fault code on a Viessmann boiler indicates a safety lockout caused by a flame failure. The boiler attempted to… Read more →