Your boiler's internal computer is having trouble processing electrical signals correctly, which is preventing it from running its safety and efficiency tests.

Emissions test mode - Internal error analog converter

What causes this fault?

This fault occurs when the boiler's main brain fails to translate physical electrical signals into data it can understand. It is usually caused by an internal hardware failure within the circuit board's circuitry, meaning the boiler can no longer verify if it is burning fuel safely or efficiently. As a result, the system shuts down to prevent any unpredictable behavior.