Did some additional diagnosis today. It throws a P0480 code (cooling fan 1 Cntrl Ckt). But I also Jumped the relays W/ a peice of wire and I can get both fans to come on in low and high so ither there is some bad wiring or the pcu has got somthing wrong W/ it. It is going to the dealership today I,ll let you know what it was when we get it back.

 

Got an answer the dealership found a short in the wire going from the pcm to the junction box that has the realay's. The teck said it is common in the Impallas due to wear threw in that section of the wiring harness. So I don't know if that would be the same for a Monte Carlo. But something to look into.

 

I have been experiencing similar issues after driving a short distance and coming to a stop my temp gauge shoots up close to overheating if i start to drive it will go down but not much. i put in a 180 degree thermostat about a year ago. it would hold at 180 for a long time but the weather recently changed in vegas to hotttt so im not sure why im seeing such a rapid heat increase. Im opting for a new thermostat along with a radiator flush and possibly high speed fans.