E4
FAULT CODE
Viessmann
Burner Start Flame Signal Too Weak
Medium Severity
DIY Check Possible
The burner attempted to start but the ionisation signal (flame detection) was too weak or missing. Common ignition fault across Vitodens range.
Cold Weather Note
In cold weather, check for a frozen condensate pipe before calling an engineer.
Step-by-Step Fix Guide
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Step 1
Check gas supply
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Step 2
Check for frozen condensate pipe in cold weather
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Step 3
Reset once
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Step 4
Call a Gas Safe engineer if fault persists — the ignition electrode or gas valve may need attention
Gas Safe Reminder
Work on gas appliances must be carried out by a Gas Safe registered engineer. The steps above cover safe checks a homeowner can perform - any internal component replacement requires a qualified professional. If in doubt, always call an engineer.