Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect gas valve electrical connector plug
(held by one centre screw) from gas valve

Measurement:

Test 1:
Measure resistance across the
top and bottom pins on the gas valve.
Expected resistance approximately 4.2 KOhms.
Test 2:
Measure the resistance from the top pin on the gas valve to a suitable earth point.
Expected resistance greater than 1M Ohm.