Your boiler has detected an internal wiring problem or a connection issue that is preventing it from running safely.

Faulty cable loom | Faulty or incorrect loom fitted

What causes this fault?

This fault occurs when the boiler's internal computer detects a mismatch or a break in the electrical wiring harness that connects the main components. The most common reason is that a wire has become loose, damaged, or was incorrectly connected during a previous repair, preventing the system from communicating safely. In some cases, it can also be caused by using an incorrect wiring loom that doesn't match the specific model of your boiler.