BoilerFaultCodesThe 6 most common faults
01
No light High DIY-safe
Your boiler has lost power completely and the display screen is blank, meaning it cannot start the heating or hot water process.
What to try first
Check if other appliances in the house have powerEnsure the boiler's fused spur switch (usually near the boiler) is turned onCheck your home's main consumer unit (fuse box) to see if a circuit has tripped
02
360 High Engineer
Your boiler's computer brains are having a communication problem because an incorrect or faulty internal component has been detected.
Full guide for 36003
Fast flash High Engineer
Your boiler has detected a critical internal communication or hardware error and has locked itself out for safety.
Full guide for Fast flash04
lockout High Engineer
Your boiler has stopped working because it cannot detect a flame, likely due to an interruption in your gas supply.
Full guide for lockout05
E01 High Engineer
Your boiler is failing to light the flame or keep it running, which means it cannot produce any heating or hot water for your home.
Full guide for E0106
E04 High Engineer
Your boiler's water pump is failing to move hot water around your system, meaning your radiators and taps will not warm up.
Full guide for E04on the Worcester Bosch 26 CDi Xtra
Internal Glass FusePrinted Circuit Board (PCB)TransformerHeat Control Module (HCM)Main PCBFan
Based on parts cited in our fault code database. Your engineer will confirm what's actually needed after diagnosis.
Call a Gas Safe engineer if…
- You can smell gas or see signs of a leak
- The Worcester Bosch shows an Emergency or High severity code
- The boiler keeps locking out after repeated resets
- You've tried the DIY checks and the fault hasn't cleared
- There's visible water leaking from the boiler
- The flame is yellow or orange instead of blue