?
I have some notes at work somewhere but I think the purple and white is for fuel pump power when cranking only, then the AFM takes over powering it once the engine is running.
Please someone correct me if I'm wrong! I will check my notes tomorrow.
Mick.
I had a look at my 75 3.0. That sensor on my car features Black (N) and a Brown (M) insulated wires. No Purple / White (ZB) wire in or about the thermostat housing.
On the workshop manual electrical schematic PA371400000000 "Door-lock Device", a "ZB wire loops from the door lock unit (N11 / pin 7) to the front left door lock motor (P11 / pin 2). Could it be possible your purple/white (ZB) wire is not original? Has an aftermarket immobiliser been added and somehow used the door lock function to drive some half arsed ignition killer?
Colin