Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove plug from diverter valve motor
Pull X4 back slightly to expose test pins

Measurement:

Check for continuity (zero resistance) of each of the
5 wires running between X4 and the disconnected plug.
(refer to table below for which pins to test between for each wire).
Inspect harness and connectors for good overall condition.