So this morning I had my cooling system completely flushed. They used the machine to flush out all the dexcool crap. Used the green stuff to refill, and also replaced the thermostat with a stock one from OReilly's. Well now my heater finally works great.

But now the fans will not come on when the car gets hot. If I turn on the AC or heat/defrost, they will come on. But idling, slow traffic, the car will just keep rising and overheat. Took it to autozone and it is throwing codes 1641 and 1642. Please any help with this matter is greatly appreciated.

 

Visit http://shbox.com He has a very detailed overheating diagnosis for the LT1. Those codes are for the relays, but probably good if they're coming on with the AC on. Gotta be something the shop did - air in the system, forgot to connect the sensors, etc.

 

I watched them, the sensors are connected. Would air in the system cause this?

 

air in the system would just cause over heating but not you fans turning on and off.Check your fan relay and maybe your ECT sensor just crapped out on you.

 

Would that be the Coolant Temp sensor right? Which one would it be most likely, the one on the water pump or the other? Is there a way to test the sensor?

 

http://shbox.com/1/4th_gen_tech2.html#ect

 

Well I replaced the coolant temp sensor in the water pump. That seemed to fix the problem. Thanks