On a efi the ecu uses a O2 sensor I have not played around with a zd so I'm not sure what it uses but you did say you disagreed that the coolant temp does play a role, I never said up to or during NOT I said simply it was significant bacuse it affected timing and duration of injection and compared it to carby and efi coz the gq td has no ecu where the zd does and meant it as the coolant temp sensor does not play a major role on the td42, unless of course you're talking the td42ti then thats a different story lol.
What does the zd use at NOT ??
Lol! All manufacturers have this feature to prevent you from blaming their design when you coock your motor after it has over heated. All its meant to do is take a load off the motor to help cool it down.
A couple of weeks ago I was at a b'day in the high country and my radiator was blocked so my trol was overheating so on a 35* day I had the heater on flat out to control my water temps.... to say my mrs was impressed was an understatement hahahah
The sensore is on the lower thermostat housing where the bottom hose connects to the motor, in between it and the exhaust. On petrols they have a thermal fan switch on the side of bottom hose tank which kicks in the auxiliary fan when the engine over heats