Set Appliance State:
Set Multimeter to Resistance 
Isolate Mains Power to appliance as per TOPs P4
Remove both ends of the diverter valve harness, from the diverter valve and from X4 on the PCB
at the back of the lowered facia.
Remove both ends of the diverter valve harness, from the diverter valve and from X4 on the PCB
at the back of the lowered facia.
Measurement:
Measure the resistance of each of the 4 wires of the harness.
Isolate as per TOPs P4
and refit as necessary