Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect the ignition lead from the spark
generator and from the ignition electrodes
(The spark generator will slide up and out to allow more space)
Disconnect the upper earth wire from the spark generator

Measurement:

Measure the resistance between the two
connectors for the ignition lead.
Resistance of greater than 1M Ohm expected.
Inspect the overall condition of the ignition lead
for any signs of shorting or damage.