Set Appliance State:

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

Measurement:

Measure the resistance of the pink, blue, black and brown wires of the harness from the diverter valve plug to connector X2.
Note:
If the new style of diverter valve is fitted, disconnect the adaptor and test from the original harness as shown. The adaptor is not available as a spare part.