Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect the display harness from X40 on the main PCB and at the display board

Measurement:

Measure for continuity (zero resistance) through each of the 5 wires of the harness, in turn.
Inspect the harness and connectors
for good overall condition.