Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector from spark generator

Measurement:

Check for continuity (zero resistance) of the blue and brown wires running from the disconnected plug to X2/X1 on the PCB.
Brown = X2 Pin 4.
Blue = X1 Pin 2.
Inspect harness and connectors for good overall condition.
Note:
Wires may be multicoloured.