Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector X2 from the PCB and
electrical connector to the diverter valve

Measurement:

Measure the resistance across each wire of the diverter valve harness, pins 7,8,17,18 of X2 to the corresponding wire on the diverter valve connector. (e.g. blue lead X2 connector to blue lead diverter connector)
Expect continuity / zero resistance on each wire.
Also visually inspect the condition of the harness.
Note:
Numbering is present on connector X2 to aid identification of wires.