Set Appliance State:

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

Measurement:

Measure the resistance between pins 2 (white) 3 (red) 4 (black) and 5 (brown) on Connector CN31 to the corresponding pins on the diverter valve motor connector.
Expect continuity / zero resistance on each test.
Also visually inspect the condition of the harness.