Your boiler's main internal computer cannot find its unique identity chip, causing the system to stop working for safety.

Code plug not detected.

What causes this fault?

This fault occurs when the boiler's control board loses communication with a small, specialized data chip inside the unit. The most common reason is that the chip has worked loose due to minor vibrations over time, or the internal circuitry of the Printed Circuit Board has failed, preventing it from reading the chip's identity.