Set Appliance State:
| Isolate Mains Power to appliance as per TOPs P4 |
Set Multimeter to Resistance 
Disconnect main solenoid wires
(purple and brown connectors) from the gas valve
Disconnect connector ST16 from the PCB
(purple and brown connectors) from the gas valve
Disconnect connector ST16 from the PCB
Measurement:
Test 1:
Check resistance across pins 7 & 8 (brown wires)
and 9 & 10 (violet wires) on ST16 to the
corresponding connector for the gas valve.
Expect continuity (zero resistance)
on each of the 4 wires.
Test 2:
Inspect the general condition of the harness and plugs and
check the resistance of each wire to a suitable earth point.
Expect greater than 1M Ohm on each wire.
Check resistance across pins 7 & 8 (brown wires)
and 9 & 10 (violet wires) on ST16 to the
corresponding connector for the gas valve.
Expect continuity (zero resistance)
on each of the 4 wires.
Test 2:
Inspect the general condition of the harness and plugs and
check the resistance of each wire to a suitable earth point.
Expect greater than 1M Ohm on each wire.
Isolate as per TOPs P4
and refit as necessary