Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Disconnect FW100 or its wireless receiver from the boiler (this is done by unscrewing the upper panel then sliding the receiver up and out of the front of the appliance)
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Reset appliance as necessary.
Does the boiler now operate or return to fault code?