Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector CN2 from the main PCB
Remove the gas valve connector

Measurement:

Test 1:
Measure the resistance between Pin 1 (Blue) on CN2 and the Blue on the gas valve connector.
Expect continuity (zero resistance).
Test 2:
Measure the resistance between Pin 2 (Brown) on CN2 and the Brown on the gas valve connector.
Expect continuity (zero resistance).
Also inspect the condition of the harness visually for general condition and any signs of damaged insulation.