Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove the plug from the gas valve and unplug the
connector marked X20 from the PCB
connector marked X20 from the PCB
Measurement:
Check harness for continuity across the gas valve leads and the right hand two positions (blue and red) of X20.
Check the general lead condition.
Check the general lead condition.
Isolate as per TOPs P4
and refit as necessary