BoilerFaultCodesWhat the manual says
Manufacturer manualBoiler at lockout.
From this model's manual
Verified against the Envoy 3040506080 installation & service manual.
What causes this fault?
This fault occurs when the boiler's control board fails to detect a stable flame after several attempts to ignite. The most common reasons are a worn-out ignition spark that can no longer light the gas or a dirty sensor that cannot 'see' the flame even if it is burning. In some cases, it may be caused by an inconsistent gas supply or a failing gas valve that isn't opening correctly.
Engineer required
This is a high severity fault. Stop using the boiler and call a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
Find a Gas Safe engineer
Search the official register →
Boiler cover options
Avoid the next call-out bill
A cover plan would handle faults like 8 (Flashing): no call-out fees, no surprise bills.
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.