Your boiler is having trouble communicating with an optional external control accessory, meaning it cannot receive or send specific remote commands.

Incorrect LON communication module

What causes this fault?

This fault occurs when the boiler's internal computer fails to recognize or communicate with the plug-in communication module. The most common reason is that the module has either worked itself loose, been installed incorrectly, or has suffered an electrical failure that prevents it from sending data to the main control board.