Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector CN1 from the interface PCB

Measurement:

Measure the resistance between the pins on CN1 and the terminals on the incoming mains terminal block as listed in the table below:
The Voltages should conform to the table below:
Connector CN1Incoming terminal strip
Pin 4 (White)Terminal 1
Pin 5 (Yellow) Terminal 3
Pin 6 (Black)Terminal 2

Expect continuity on each test.
Also visually inspect the harness for general condition and any signs of damaged insulation.