Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Continuity Set meter to measure Continuity
Remove the black leads from the gas valve and unplug the large (20 way) connector for the right hand side of the PCB

Measurement:

Check harness for continuity across the black gas valve leads at positions 3, 4, 5 & 6 at the PCB end to the gas valve connectors.
Check the general lead condition.
Reconnect lead after test.
Note:
1. Ensure a good, firm contact is made with the gas valve lead connectors.
2. Colours may vary from those shown but the terminals will remain the same.
3. There are two types of gas valve for this appliance but the test remains the same for either valve.