silverado auto dim/compass/temp mirror

Hey guys I just installed the factory rear view mirror with the built in lcd for the compass and temp meter. I got the mirror wire up (factory harness hidden in headliner, no wiring needed). The compass works fine, but the temp is displaying OC which I beleive is because I dont have the temp sensor plugged in. I DO have it, thing is I have no idea where it goes. I know somewhere infront of the radiator, but i guess my real question would be is if the truck has the wiring for this sensor installed at the factory (since the 7 pin plug was installed at factory)and is just hidden somewhere, or if I need to run some wires through the firewall to connect to the mirror? thanks

hi, we know it's a silverado...what year?

Whoops, forgot to mention that. Its a 2001