Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Unplug the lead from the spark generator and X21 of the PCB

Measurement:

Measure for continuity along the blue and brown wires between each end of the spark generator lead.
(The brown is the top connection, furthest away from the cable)
Expect continuity