Set Appliance State:
Set Multimeter to Resistance 
Isolate Mains Power to appliance as per TOPs P4
Remove plastic cover from gas valve
Remove plastic cover from gas valve
Measurement:
Remove the Red spaded wire and the Blue spaded wire from the Pilot Solenoid on the Gas Valve.
Measure the resistance across the Solenoid.
The Solenoid resistance should be approximately 2.1kOhms.
Measure the resistance across the Solenoid.
The Solenoid resistance should be approximately 2.1kOhms.
Isolate as per TOPs P4
and refit as necessary