Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect the harness from the display PCB

Measurement:

Measure the resistance between the pins on X6 and the display harness connector as listed below:
Pin on connector X6Display harness connector
1 (Black)Black
2 (Red) Red
3 (White)White
4 (Green)Green

Expect continuity / zero resistance on each of the wires.
Also visually inspect the condition of the harness.