BoilerFaultCodesVaillant P.2 Fault Code
Also written as P2 — same fault.
The Vaillant P.2 fault code means: your boiler is currently running a background self-test to check it can operate safely at its lowest power setting.. It appears on 14 Vaillant models in our database.
Technical description: Test program where the appliance is operated with minimum gas volume (ignition gas volume) after successful ignition
What causes the Vaillant P.2 fault?
This code appears when the boiler automatically performs a internal calibration test to ensure it can sustain a stable flame at the lowest possible gas level. It is a normal part of the boiler's software routine and happens automatically after the burner ignites to verify efficiency and safety. You do not need to take any action as the boiler is simply checking its own homework before continuing to heat your home.
DIY fix possible
Wait for the test to complete automatically (usually takes 15 minutes)Press the 'Back' or 'Reset' button if the boiler appears stuck after 20 minutesTurn the power off and back on at the fused spur switch to restart the system
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Vaillant models that show the P.2 fault code
Click a model for the full fault code list and model-specific repair notes.
Source
Vaillant P.2 fault code information on this page is sourced and cross-checked against the official Vaillant service / installation manuals for each affected model.
Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026