BoilerFaultCodesYour boiler’s internal computer has lost contact with a small identification chip that tells it how to operate correctly.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Code plug not detected
What causes this fault?
This fault occurs when the boiler's main control board can no longer read the small identification chip, known as a code plug, which contains the unit's specific settings. The most common reasons are a loose connection caused by natural vibrations over time or a physical failure of the chip or the circuit board itself.
Engineer required
This fault requires a Gas Safe registered engineer. Do not attempt gas-related repairs yourself.
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 b1 — 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.