Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect the lead from the gas valve

Measurement:

Test 1:
Measure the resistance between the pins on the gas valve.
Resistances should be approximately as in the table below.
PinsResistance
1 - 36.7 kOhms
3 - 4 880 ohms

Test 2: Resistance to Earth
Measure the resistance between pin 1 and pin 2 on the gas valve.
Expected resistance greater than 1 MOhm.
Note:
The pins on the gas valve should be numbered.