Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove the two connectors from the gas valve

Observation:

Test 1.
Measure for resistance across the top two gas
valve solenoid terminals.
Expected resistance approximately 400 ohms.
Test 2.
Measure for resistance across the bottom two gas
valve solenoid terminals.
Expected resistance approximately 180 ohms.
Test 3:
Measure the resistance between one pin on each of the solenoids to a suitable earth.
Expect a resistance of 1 Mohm or greater.
Are the resistances measured as expected?