My temp gauge shoots to max and "Check gauges" comes on with some beeping. Turning the truck off and then back on puts everything back to normal. What the????

Ive tried with and without tunes installed, it did it before and after my radiator fluid change, and I am about out of ideas... Anyone?

I have a "rattle" noise sometimes at startup and under light load at low speed. I always thought it was phasers but who knows anymore...

 

Better get your battery checked. This is often the sign it is getting ready to fail.

 

Mine did the same exact thing.....would overheat so I'd turn it off and turn it back on and it would go back to normal. Had the rattle you describe too. I think it was my catalytic converter going bad that was making the rattling noise because I got the low catalyst efficiency CEL shortly after the rattling started. Cat was covered by the emmissions warranty and the dealership ended up putting in a new thermostat. Rattling noise sounded like marbles rolling around in a soup can almost.

 

You could also have damaged wiring at or near your coolant temp sensor