Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Disconnect the lead from the diverter valve motor

Measurement:

Measure the continuity of each of the wires in the harness from the PCB to the diverter valve.
Expect continuity (zero resistance) through each wire.
Inspect the harness and connectors for good overall condition.