BoilerFaultCodesThe 6 most common faults
01
133 High DIY-safe
Your boiler has failed to ignite or lost its flame, meaning it has temporarily stopped working to keep you safe.
What to try first
Check that your gas supply is working by testing another gas appliance like the cooker.Make sure your prepaid gas meter (if you have one) has credit.Press and hold the boiler's reset button for 1 to 3 seconds to try restarting it.
02
118 High DIY-safe
Your boiler has detected that the water pressure inside the heating system has dropped too low.
What to try first
Locate the filling loop underneath your boiler or near the hot water cylinder.Open the valves slowly to let mains water into the system until the pressure gauge reads between 1 and 1.5 bar.Close the valves firmly and check the gauge holds steady.
03
09 High Engineer
Your boiler has lost communication with its internal electronic brain, causing it to shut down for safety.
Full guide for 0904
15 High Engineer
Your boiler has lost communication with its main electronic brain, so it has safely shut down to prevent unexpected behaviour.
Full guide for 1505
110 High Engineer
Your Baxi boiler has temporarily stopped working because it has lost proper internal communication between its main electronic parts.
Full guide for 11006
384 High Engineer
Your boiler has lost safe communication with its internal computer board, so it has safely shut down to prevent damage.
Full guide for 384on the Baxi 618 SYSTEM
Ignition electrodeGas valvePCBPressure relief valvePressure sensorExpansion vessel
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 Baxi 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
Boiler cover options
Avoid the next call-out bill
Monthly cover means no unexpected bills when your boiler breaks down.
Approved partner
Get a quote →
Domestic Appliance Guard
Unlimited call-outs, 24/7 helpline, no price-hike promise
Affiliate links. We may earn a commission at no extra cost to you.