How much does it cost to fix boiler error code Red LED illuminated (TTB)?

Typical repair cost for the boiler Red LED illuminated (TTB) fault is £120-250 including labour.

Red LED illuminated (TTB) Emergency

Boiler Fault Code Red LED illuminated (TTB)

Also written as REDLEDILLUMINATEDTTB — same fault.

Reviewed by the BoilerFaultCodes Editorial Team Last reviewed 27 April 2026

Fault code Red LED illuminated (TTB) appears across 1 boiler brand and 1 models. The exact meaning varies by manufacturer — pick your boiler brand below to see the model-specific fix.

Most common meaning Your boiler has detected potentially dangerous exhaust fumes backing up into your home due to a blocked or obstructed chimney or flue, and has safely shut itself off to prevent carbon monoxide poisoning. (As reported on Potterton Kingfisher MF 40-100)

Pick your boiler brand for the Red LED illuminated (TTB) fix

Potterton Red LED illuminated (TTB) 1 model

Source

Information for the Red LED illuminated (TTB) fault code is sourced from the official service / installation manual for each model that displays it. Read more about how we source fault codes →

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed 27 April 2026