Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector CN5 from the display PCB

Measurement:

Measure the resistance between the pins on CN5 and the terminals on the incoming mains terminal block as listed in the table below:
Connector CN5Incoming terminal strip
WhiteTerminal 1
Yellow Terminal 3
BlackTerminal 2

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