Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove connector X10 from the PCB
Remove connector from the DHW flow sensor
Remove connector from the DHW flow sensor
Measurement:
Measure the resistance across each of the wires of the DHW flow sensor harness between connector X10 and the DHW flow sensor connector.
Expect continuity / zero resistance on each wire.
Expect continuity / zero resistance on each wire.
Isolate as per TOPs P4
and refit as necessary