Your boiler's internal computer chip is either missing or has failed, meaning the system doesn't know which specific model it's supposed to be.

Incorrect code plug detected – the code plug needs replacing

What causes this fault?

This fault occurs when the boiler's memory chip, which holds the specific instructions for your model, is either damaged or has become loose. Without this physical plug being correctly identified by the control board, the boiler cannot safely operate and will shut down to prevent damage. The most common reason is a hardware failure within the plug itself or a communication error starting in the main circuit board.