code 16 is usually battery over voltage. have you used a handset to set the voltage of the controllers to the actual battery voltage rather than a default setting for 36&48 volts? what happens in a dead battery 48 volt truck if the setting is the default, the controller may think it is a too hot 36 volt battery rather than a too dead 48 volt battery. that would be my assumption. setting it to the actual battery/truck voltage (function 17 I think, off the top of my head) should fix part of the problem and the other part will be fixed when the battery is good.