Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect PCB to PCB harness from CN104 on the control PCB and CN100 on the ignition PCB

Measurement:

Check for continuity (zero resistance) between each of the 7 wires running between the two PCBs.
Inspect harness and connectors for good overall condition.
Note:
Wires are not all on the same pin number across both
harnesses, refer to table below.