Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Gain access to PCB (use Insulation Mat as required)

Observation:

Inspect the 5 wire harness running between J2 on the control PCB and J1 on the ignition PCB.
Check each wire is in good condition, that they are fitted securely to the plugs and that the plugs are fully pushed home.