Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect connector J1 from the control PCB

Measurement:

Check the condition of the harness between the external controls terminal block and connector J1 at the control PCB.
Check for continuity between:
Red on J1 to red on terminal block,
Grey on J1 to grey on terminal block,
Blue on J1 to blue on terminal block.