ABS light comes on when parking brake applied

couple of odd things going on with the brakes:
1) if you apply the parking brake the abs light comes on

2) have low pedal, but if you pump it up it gets firm. The master cylinder diagnosis was good, so its not that.

3) abs light has come on but when you restart car it goes off, than a couple of days later will come on again; and yet again go off.

there are no leaks, system was properly bleed and pads are excellent.
please tell me how to fix this stuff before I dump a bunch of money in without it fixing anything.

just wondering why a infiniti dealer would charge $289 for a lower ball joint, thats just the part! Its less than $30 at any auto parts store.