BoilerFaultCodesViessmann db Fault Code
Also written as DB — same fault.
The Viessmann db fault code means: your boiler is currently operating on a fixed schedule and is not using your room thermostat to adjust its temperature automatically.. It appears on 1 Viessmann model in our database.
Technical description: Control mode without room influence
What causes the Viessmann db fault?
This fault occurs when the electrical signal from the secondary heating zone's temperature sensor is interrupted by a short circuit. The most common reason is that the delicate internal wiring of the sensor has degraded or has been physically pinched, causing the sensor to send an incorrect electrical reading back to the main control board.
This fault is often noticed at the start of autumn when homeowners first try to turn on their secondary heating zones after the summer break.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Avoid the next call-out bill
A cover plan would handle faults like db: no call-out fees, no surprise bills.
Affiliate links. We may earn a commission at no extra cost to you.
Viessmann models that show the db fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Viessmann db fault code information on this page is sourced and cross-checked against the official Viessmann service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 7 July 2026