Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove the connector from the Aqua sensor
Remove connector X2 from the PCB

Measurement:

Measure the resistance of each of the wires in the harness to the Aqua Sensor as stated in the table below.
Pin on connector (X2)Aqua Sensor Connector
3 (Red)Red
2 (Black) Black
6 (Green)Green

Expect continuity on each of the wires.
Also visually inspect the harness for good general condition.
Note:
Each pin on the PCB connector is numbered.