Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Disconnect the ignition lead assembly connector from the spark electrode and from the PCB
Measurement:
Check resistance between each end of the ignition lead.
Zero resistance expected.
Check lead in its entirety for good condition and that it is not shorting to earth especially where it passes near the boiler casing.
Zero resistance expected.
Check lead in its entirety for good condition and that it is not shorting to earth especially where it passes near the boiler casing.
Isolate as per TOPs P4
and refit as necessary