K, so one of my geets is a SDGr 6-string bass guitar, its cheap but it plays good... usually,

Lately theres been a problem with what I think are the pick-ups, when I play for anymore than 10 or 15 minutes with it plugged in, the signal starts to fade and become quiet and/or distorted.

Now, its not the chord or the amp, those are out of the question as I've tested many, so I need some help, and by the way I'm incompetant in terms of guitar mechanics so if the answer seems obvious then have mercy.
if it's an active bass you will find a 9 volt in the back, try replacing it
I had the same problem, and was told to replace the battery. it worked.