Set Appliance State:

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

Measurement:

Test 1:
Measure the resistance between the pins
on the gas valve modulating solenoid.
Expected resistance approximately 80 ohms.

Test 2: Resistance to Earth
Measure the resistance between either pin to a suitable Earth point.
Expected resistance greater than 1 MOhm.