My 08 sierra had this same message. It wasn't hot and the antifreeze reservoir was full. The thermostat wasn't reading correctly. We had that replaced and so far so good.
under the pickup in the center of the engine block
60 to 66 PSI. Can be as low as 50 when engine is running.
Drive side of the engine....about halfway back. It will be right above the cross member running under the engine.
No less then 13.8 and no more then 14.2 Volts with engine running.
On the back side dead center location has no changed in years.
It is the round canister in the rear center of the engine, at the firewall.
If you are checking Alternator voltage, It should 12.8 volts to 14.3 with engine running. Battery voltage is 12.3---12.8 with engine off.
The 1998 Chevy Silverado pickup truck shift solenoid can be found on the left-hand side of the engine. The shift solenoid will be near the center of the transmission.
I have one with 289,000 miles with a gas engine and running like the day i bought it new
The intake manifold is bolted on the center of the engine between the 2 Valve covers.
The 2009 Chevrolet Silverado-3500HD has a V8 engine.
The 2014 Chevrolet Silverado-3500HD has a V8 engine.