Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect 4 pin connector from the programmer

Measurement:

Check for continuity (zero resistance) between pin 1 (orange) at connector X9 at the PCB to the orange wire opposite the blue wire on the disconnected plug.
Check for continuity (zero resistance) between pin 3 (orange) at connector X9 at the PCB to the orange wire opposite the brown wire on the disconnected plug.
Inspect the harness for good overall condition.