| minor truss rod adjustment
the usual cause of buzzing from 12th fret up to 15th fret is too much bow in the neck. loosen the string tension by detuning. sit in a chair or on the edge of your bed and stand the bass up on it's tailend, firmly planted between your feet, with your left foot up against the back of the bass and left knee against the neckjoint or heel. right foot against the bridge. place your left hand low on the neck near the heel or neckjoint for forward support. take your right hand and gently, but firmly push back on the front of the headstock, very---very----very gently flexing the neck ever so slightly. you're loosening the stiffness of the neck ever so slightly so you don't strip the trussrod, which you're about to adjust by tightening.
now, lay the bass flat on your work surface or bed and take your truss rod. same principle as in the rest of the "nut tightening/loosening world". RIGHTY TIGHTY--LEFTY LOOSY.
you need to tighten the truss rod 1/4 turn clockwise or to the right.
retune.
leave it alone for an hour or two.
retune again.
check string height according to specs on your bass manufacturer's website and adjust bridge saddle heights accordingly.
intonate.
that should fix it.
if you develop buzz now from 5th back down to 1st frets, you've over tightened and need to loosen maybe an 1/8 of a turn counterclockwise. | 
