Your boiler has shut down because it is unable to accurately measure the air pressure required for its burner to operate safely.

Burner blocked. Differential pressure sensor faulty. Cause: Check the differential pressure sensor and lead.

What causes this fault?

This fault occurs when the boiler's internal computer receives an incorrect or missing signal from the sensor that monitors air flow. The most common cause is a physical blockage in the burner or a failure in the electronic sensor that ensures the unit is breathing correctly for safe combustion.