my fiance has an 03 gmc envoy slt, and the tach needle as of yesterday is not in the correct position at startup and dosent move properly when the engine revs higher. its actually sitting almost stright down, and seems to move when the engine is revved but not nearly as much as it should. is this likely just a loose connection? where is the cable that monitors rpm so i can check to see if its loose? or is there a way to re-calibrate the tach? maybe unhook the battery for a period of time?