im getting a code 22 = MAP sensor. problem is i can check and im getting the full 5 volts disconnected but when i hook it abck up the manual says to check it with a tachometer, i have a snapon digital meter and i dont see a setting for tachometer. i tried to measure it the voltage way but only get 2.5 volts and putting a vacuum to it does nothing, it is new, just put it on yesterday.