Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Ensure there is no demand for either CH or DHW
Use Insulation Mat as required
Remove the diverter valve motor from the diverter body
Place the diverter valve motor in a safe location
WARNING! - Mains voltage is expected during test follow
TOPs P4 live testing procedure
Mains Power On

Observation:

Observe the diverter valve heads actuator pin as the boiler powers up.
As the boiler competes its self-check the diverter valve motor should move from the fully retracted position (DHW) to the fully extended position (CH) then fully retract again.
Note:
If the actuator is already in the extended position (CH)
you may need to repeat the test.