BoilerFaultCodesYour boiler has stopped working and locked itself to prevent damage, but it needs a second digit to identify the specific problem.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Boiler is in lockout for a specific error. Display will show a number after the L to indicate which error is detected.
What causes this fault?
This fault occurs when the boiler's internal computer detects a critical failure and enters a safety lockout to prevent further damage. It is usually triggered by a failure to ignite or a breakdown in communication between the electronic sensors and the main control board. The boiler stops running as a protective measure until the specific underlying component error is identified and resolved.
DIY fix possible
Check the display for a number following the 'L' (e.g., L2 or L5)Press and hold the 'Reset' button for two secondsCheck that your gas supply is active and credit is on the meter
Find a Gas Safe engineer
Search the official register for a qualified engineer in your area.
Gas Safe Register →Protect yourself from future repair bills
A boiler cover plan would cover faults like L — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Could it be time for a new boiler?
If repair costs are adding up, a new energy-efficient boiler could be the smarter long-term choice.
Affiliate links — we may earn a commission at no extra cost to you.