Set Appliance State:

Gas Off
Set Multimeter to Resistance Set meter to measure resistance
Isolate Mains Power to appliance as per TOPs P4
Remove plugs M3 & M5 from the board

Measurement:

Check for short circuit resistance across connector M3 connection 10 (Red) and connector M5 connection 26 (Red).
Replace plugs M3 and M5 after test.