What should the MAP sensor be reading with the engine not running??

 

The smart *** answer is atmospheric pressure. I think what you are looking for though is close to zero. Generally, depending on altitude and atmospheric conditions it's going to read -1 or -2 psi.

 

Yeah, I first thought atmospheric pressure.. which would be 14.7 PSI at sea level, and about 250 feet above sea level. eather that or 0 PSI. for some reason it is reading 0.6 PSI i must have the wrong GM 3 BAR Map sensor????

 

That reading is completely normal.