Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Continuity 
Measurement:
Remove the short harness connecting, J1 (black connector) on the ignition PCB and J2 (black connector) on the main PCB.
Check the continuity and inspect the harness for signs of damage.
Check the continuity and inspect the harness for signs of damage.
Isolate as per TOPs P4
and refit as necessary