Your boiler has detected a fault with the sensor that monitors exhaust fumes, causing the system to shut down for safety.

Flue gas probe short-circuited

What causes this fault?

This fault occurs when the internal sensor responsible for monitoring the temperature of exhaust gases identifies an electrical short-circuit. The most common reason is that moisture or heat stress has damaged the sensor's internal wiring, causing it to send an incorrect signal to the main control board. As a result, the boiler shuts down immediately to prevent potential damage to the flue system or the heat exchanger.