Your boiler's gas control mechanism has stopped moving correctly, which means the system cannot safely regulate the fuel it needs to stay alight.

STEP MOTOR FAILURE: MOTOR CONNECTION OR MOTOR FAILURE.

What causes this fault?

This fault occurs when the small internal motor that regulates the gas supply fails to move into the correct position. The most common reason is that the motor's internal components have worn out or become physically stuck, meaning the boiler can no longer safely control the amount of fuel entering the burner.