Just what specifically is responsible for the ECU knowing the engine is warmed up? What sensors, etc., on the car supply this info?

Thanks

jeryj

 

The Water temp switch located on the drivers side of the radiator probably tells the ECU if its too hot, and a varible water temp sensor located near the thermostat, probably tells the engine the actual temp for fuel enrichment sake...

 

The one on the radiator is for the cold start assist system. The one on the water pump housing is what the ECU reads.