Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove the gas valve harness from the
Ignition PCB but leave connected to the gas valve
Ignition PCB but leave connected to the gas valve
Measurement:
Measure the resistance across the blue and brown wire pair in position 4 & 5.
Expect approximately 4 Mohms.
Isolate as per TOPs P4
and refit as necessary