BoilerFaultCodesViessmann E01 Fault Code
The Viessmann E01 fault code means: your boiler is not lighting properly and has locked itself out for safety, which means you currently have no heating or hot water.. It appears on 1 Viessmann model in our database.
Technical description: Burner does not start. No flame signal after the safety time has elapsed. (Reset required: Turn control knob 'Reset' to the right until 'CL' appears, then turn back).
What causes the Viessmann E01 fault?
This fault occurs when the boiler tries to ignite the gas to create a flame but fails to detect one within a safe time limit. The most common reasons include a lack of gas reaching the burner, worn-out ignition components that can't create a spark, or a dirty sensor that cannot 'see' the flame even if it has lit.
This fault is frequently seen during extreme cold snaps, as the external condensate pipe can freeze and block the system, preventing the boiler from lighting.
DIY fix possible
Check that your gas pre-payment meter (if you have one) has credit.Ensure the gas stop tap is fully open and other gas appliances like your hob are working.Restart the boiler: Turn the control knob to the 'Reset' position until 'CL' appears on the screen, then turn it back to its original position.
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Gas Safe Register →Viessmann models that show the E01 fault code
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Source
Viessmann E01 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 27 April 2026