BoilerFaultCodesVokera d1 & d2 Fault Code
Also written as D1D2 — same fault.
The Vokera d1 & d2 fault code means: your boiler has stopped working because the pipe that carries waste water away is likely blocked or frozen, causing water to back up inside the unit.. It appears on 4 Vokera models in our database.
Technical description: Problem with condense trap/pipe/ sensor. Call engineer.
What causes the Vokera d1 & d2 fault?
This fault occurs when waste water produced during the heating process cannot drain away from the boiler, causing it to back up inside the internal trap. The system detects this rising water level via a sensor and shuts down the boiler to prevent internal flooding or damage. The most common reasons are a blockage in the internal trap or an obstruction in the external pipework leading to a drain.
This fault is significantly more frequent during freezing winter temperatures, as the external waste pipe can freeze solid and prevent water from leaving the system.
DIY fix possible
Check the white plastic pipe outside for ice and pour warm (not boiling) water over it to melt any blockages.Ensure the end of the external pipe is not submerged in a drain or blocked by debris.Restart the boiler using the reset button once the pipe is clear.
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Gas Safe Register →Vokera models that show the d1 & d2 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vokera d1 & d2 fault code information on this page is sourced and cross-checked against the official Vokera service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026