Nissan Repair: 2002 Nissan Maxima, negative battery cable, neutral safety switch

Question
My check engine light recently came on.  I had it diagosed and it came back as having a vehicle speed control sensor problem and neutral position switch problem.  I changed both and had it re-diagnosed after the light came back on and showed another neutral position switch problem.  When i put my car into drive (D), the drive(D) and (2) light comes on and the car wont shift out right.  Sometimes if i drive for a little while the (2) light goes off and the car shifts out perfectly.  If i wiggle the wires a little then the light may go off only to come right back on in a few minutes.  Do i need to change the wiring harness?

Another problem im having is with power.  My battery wont hold a charge and ive gone through two brand new alternators.  While driving my dash light will "blink" or flicker too. Should the wiring harness be changed?  could there be a short in the wires causing the problems?

PLEASE HELP!!!

Answer
Vic,

The harness plug at the neutral safety switch should be inspected to see if the pins are damaged or coming a part.  Also, remove the negative battery cable and then disconnect and reconnect the ECM harness.  Both of these are common problems for issue you describe.  

For the alternator please check and see if the power feed wire from the alternator to the battery and see if it is damaged or corroded.  I would go to Autozone or Checker and have them perform a free electrical inspection.  They will know if the alternator is defective or if there is a connectivity problem at the positive terminal of the battery.  This is where the charge line of the alternator feeds to...