Your boiler's internal electronic computer chip is either missing, loose, or incompatible with the unit's software.

Code plug number: Coding plug number.

What causes this fault?

This fault occurs when the boiler's control system cannot communicate with its 'identity chip,' which tells the unit its specific model and power settings. This usually happens if the chip has vibrated loose from its socket on the main circuit board or if the chip itself has suffered an internal electrical failure. In some cases, a power surge may have corrupted the memory or damaged the printed circuit board where the chip is housed.