BoilerFaultCodesYour boiler has detected an internal software conflict or an incorrect configuration chip, preventing it from operating 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 version: Coding plug version.
What causes this fault?
This fault occurs when the boiler's main control board cannot communicate correctly with the small electronic chip that tells it which specific model it is. The most common reason is that the coding plug has become loose, damaged, or is incompatible with the circuit board, leading the system to shut down for safety. In some cases, this happens following a power surge or if the internal memory on the main board has failed.
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 1-E4 — 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.