2000 Chevy Blazer

See if there is ahole in the duct betwen teh sensor and ithrotlle. Also check your battery as it may be going bad. That will screw up a computer. If the cam sensor is bad the tach probably won't work so all of htem need to be checked to see if they are anygood. The scanner will show a temp becuase it only checks the sensor. You may have a bad guage but that needs to be checked out as it could be a bad connection or broken wire.