Set Appliance State:

Gas Off
Set Multimeter to Resistance Set meter to measure resistance
Isolate Mains Power to appliance as per TOPs P4
Unplug connector CN1

Measurement:

Measure resistance across connection 8 and connection 9 (Grey wires).

This should be approximately 130 Ohms.
Replace connector CN1.
Note:
This test should be carried out on the disconnected connector not on the PCB.