Set Appliance State:
Set Multimeter to Resistance 
Isolate Mains Power to appliance as per TOPs P4
Remove the main control box cover to expose the control PCB
Disconnect ignition electrode leads from the ignition electrodes and the control PCB
Remove the main control box cover to expose the control PCB
Disconnect ignition electrode leads from the ignition electrodes and the control PCB
Measurement:
Measure for continuity (zero resistance) between the ends of the lead running from the PCB to the spark electrode.
Inspect the lead for good overall condition.
Inspect the lead for good overall condition.
Isolate as per TOPs P4
and refit as necessary