Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove ignition electrode from combustion door
Disconnect ignition lead from the PCB

Measurement:

Measure the resistance of the ignition electrode and lead.
Expect continuity / zero resistance.
Thoroughly inspect the ignition electrode and lead for cracks / damage to the ceramic, distortion, damaged insulation on the lead, overall condition and ensure spark gap is approx. 5mm.