Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector X51 from the PCB
Remove connector from the Display PCB

Measurement:

Measure the resistance across each of the wires in the harness.
Expect continuity / zero resistance on each wire.
Also visually inspect the condition of the harness.
Are the resistances as expected and
is the harness in good condition?