Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove connector X6 from the PCB

Measurement:

Test 1:
With hot tap fully open measure the resistance across pins 1 & 2 of connector X6.
Resistance should read short circuit.
Test 2:
Turn off the DHW tap and repeat the test.
Resistance should read open circuit.