High Lockout
E28 on Potterton Promax Combi HE Plus

Your boiler's internal computer brain is either faulty or has been replaced with the wrong software version for your specific model.

Reviewed by the BoilerFaultCodes Editorial Team · Last reviewed

Call an engineer soon

Book a Gas Safe engineer within 24 to 48 hours. Your boiler may be unsafe or could break down completely if left.

Technical description

Incorrect PCB Fitted

What causes this fault?

This fault occurs when the boiler's main control board fails to recognise the hardware it is connected to, often due to a communication breakdown between internal components. It most commonly happens if a replacement part has been installed without being correctly programmed, or if the chip that stores your boiler's specific identity has become corrupted or loose.

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.

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Related fault codes

E160View →

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