Engine/Transmission (1998.5 - 2002) Grid Heater Question

[HookMeUp]

Ok I can understand the grid heaters come on in the morning, wait to start light, and then cycling after it is started. But what I don't understand is when the truck is at normal operating temperature and then shut it down for long enough to go into a building. That when you come back out to start it, no wait to start light, but after starting it up the grid heaters will cycle.

 

[PC12Driver]

If the intake air charge is less than about 70*F, the grids will enter their post-start mode for 3 minutes or 17-ish-mph, whichever comes first.



So when you re-start the truck, the IAT sensor (located toward the back of the cylinder head) will "see" temps above 70*F and not trigger the pre-start grid heater mode. Then once the engine lights and sucks the cold outside air into the intake, the post-start mode kicks in.