BoilerFaultCodesThe 6 most common faults
Your boiler's internal computer system has lost its configuration settings and no longer knows how to coordinate the heating system.
Why it happens: This fault occurs when the main brain of the boiler loses its ability to lead the communication between different internal electronic parts. It is usually caused by a physical break in the wiring connections or a software glitch within the circuit board that prevents it from acting as the 'central manager' for the system.
Locate the main power switch for the boiler and turn it off.Wait for approximately 60 seconds.Turn the power back on and press the 'Reset' button on the front control panel.
Your boiler has identified a minor internal timing error, often related to the programming board or a sensor that is out of range.
Why it happens: This code appears when the boiler has been manually put into a specialized service mode, such as a chimney sweep test or a manual calibration check. It is triggered by a user or engineer adjusting the settings to run the burner at a specific output for a set duration. Once the programmed time for this test elapses, the boiler will automatically return to its normal heating operation.
Wait for the timer to count down and the code to disappear naturallyCheck that you haven't accidentally entered a test mode via the control panelIf the code persists for over an hour, try a simple reset of the boiler
Your boiler has lost communication with a sensor that monitors water temperature moving through your heating system, which may prevent it from heating your home efficiently or at all.
Why it happens: This fault occurs when the boiler loses communication with the sensor responsible for tracking water temperature in the main mixing chamber of your plumbing. The most common reason is that the sensor itself has failed internally or the wiring connecting it to the boiler's main control board has become loose or damaged. Without this data, the boiler cannot accurately balance the heat output for your home.
Full guide for 52:0Your boiler has detected an internal electrical communication error or a fault with one of its main control components, which is preventing it from running properly.
Why it happens: This fault occurs when the boiler's internal computer system fails to communicate with the sensors and components that control the heating process. It is typically caused by a malfunction within the main circuit board or a loose connection in the wiring that prevents the boiler from receiving the safety signals it needs to fire up.
Full guide for 53:0Your boiler's internal computer is reporting an electrical fault with the pump that circulates hot water to your radiators, meaning your heating may not turn on correctly.
Why it happens: This fault occurs when the boiler's main control board loses the electrical signal required to run the external pump that moves water through your radiators. The most common reasons are a complete mechanical failure of the pump motor, a loose connection in the wiring, or a fault within the internal control board itself.
Full guide for 53:2Your boiler is struggling to heat your hot water tank because it cannot detect or communicate with a required component or sensor.
Why it happens: This fault occurs when the boiler's control system loses its connection to the sensor responsible for monitoring your hot water cylinder. The most common cause is a faulty temperature probe or a break in the wiring that prevents the boiler from knowing how hot your water is. Without this information, the boiler stops heating the water as a safety precaution to prevent overheating.
Full guide for 58:0on the Viessmann Vitodens 300-W
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Viessmann shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue