Your boiler's internal memory card or control chip is failing to communicate correctly with the main computer board.

Boiler chip card (BCC) service key fault

What causes this fault?

This fault occurs when the boiler's main control board loses its connection with the small plug-in memory chip that contains the unit's specific configuration data. The most common reason is an electrical communication failure caused by a loose connection or a faulty chip that has become corrupted over time.