Your boiler's internal sensor has detected that the water pressure is too high or the sensor itself is sending an incorrect reading.

Water pressure sensor signal in the wrong range (too high)

What causes this fault?

This fault occurs when the boiler's internal sensor detects that the water pressure is far higher than the safe operating limit. The most common reason is that the manual filling loop was left slightly open after topping up the system, or the pressure sensor itself has developed an electrical fault and is sending an incorrect high reading to the control board.