Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Gain access to PCB (use Insulation Mat as required)

Observation:

Check that the jumper is fitted to the three pins marked X200 and is positioned correctly.
It should be across the right 2 pins as shown if a SIT gas valve is fitted and across the left 2 pins if a Honeywell gas valve is fitted.