BoilerFaultCodesYour boiler’s internal computer has lost contact with a vital control chip, meaning the system cannot run safely and will stay locked out.
Book a Gas Safe engineer within 24–48 hours. Your boiler may be unsafe or could break down completely if left.
Technical description: Control box is defective – HCM needs checking as it might not be inserted properly or need replacing
What causes this fault?
This fault occurs when the boiler's main control board loses communication with a specific chip called the Heat Code Module, which contains the boiler's 'identity' and safety settings. The most common reason is that this module has vibrated loose or has suffered an electrical failure, meaning the boiler can no longer verify which model it is and shuts down for safety.
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 F0290 — no call-out fees, no surprises.
Affiliate links — we may earn a commission at no extra cost to you.
Worcester Bosch CDi Classic is discontinued — time for a new one?
Parts for discontinued models can be hard to find and expensive. A new A-rated boiler could save you money on both repairs and energy bills.
Affiliate links — we may earn a commission at no extra cost to you.