Set Appliance State:

Isolate Mains Power to appliance as per TOPs P4
Set Multimeter to Resistance Set meter to measure resistance
Remove the 12 pin connector from the ignition control box
Remove the white wire from the selector switch

Measurement:

Measure the resistance of the wire between pin 1 on the ignition control box connector and the selector switch connector.
Expect continuity/zero resistance.
Also visually inspect the condition of the harness.
Are the resistances measured as expected
and is the harness in good condition?