451 High

Viessmann 451 Fault Code

The Viessmann 451 fault code means: your boiler's internal computer system has encountered a processing error and cannot follow its normal startup or operating sequence.. It appears on 1 Viessmann model in our database.

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description: Error in scheduled program run monitoring
Typical repair cost £120-450 (including labour)

DIY fix possible

Locate the reset button (usually a 'R' or a power symbol) on the boiler control panel.Press and hold the reset button for at least 3 seconds.Wait up to 5 minutes for the boiler to complete its restart sequence.

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Viessmann models that show the 451 fault code

Click a model for the full fault code list and model-specific repair notes.

Source

Viessmann 451 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