Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Remove electrical connectors X2 from the PCB and
to the DHW flow sensor
to the DHW flow sensor
Measurement:
Measure for resistance across each wire of the DHW flow sensor harness, 2,3,6 of X2 connector to the corresponding wire on the sensor connector. (e.g. red lead X2 connector to red lead of flow sensor connector)
Also visually inspect the condition of the harness.
Expect continuity / zero resistance on each wire.
Also visually inspect the condition of the harness.
Expect continuity / zero resistance on each wire.
Isolate as per TOPs P4
and refit as necessary