Low voltage light came on car wouldn't start again and it's not alternator or Ba on 2000 Chrysler Town & Country

The voltage light was on a few days then we were driving radio died and after parking vehicle it wouldn't restart. got it started with a jump but van kept dying and back firing. tested alternator and battery both are good. anyone have a clue what else it could be?

Asked by for the 2000 Chrysler Town & Country
Have alt. voltage tested at the battery whith engine running! Can't be charging enough!! PCM (computer) controls the voltage, have it scanned!!!