If you are working on a BR 387 this may help.

Fault T 334

Description:
Capacitor voltage (:A14) is too low at power module 2A1 with activated main contactor

Conditions of occurrence:
Difference between battery voltage at pin :K1 and capacitor voltage at pin :A14 >4 V

Result:
Error lamp is lit in the display unit
Truck is completely deenergized

Possible causes:
Contact resistance at the fuses 2F6, 2F1 and F2
Possible defect of fuses 2F6, 2F1 and F2
Line interruption at the output (:A15, :A30) for main contactor control
Supply voltage at pin :K1 is too low (main contactor is not energized)
Main contactor K1 is defective
Power module 2A1 is defective
Emergency stop 7S1 is defective
Key switch S1 is defective
Fan 9M2 or 9M3 is defective
Contact resistance at the lines or plugs of the a.m. components

Steps to eliminate the fault:
Check fuses
Check cable harness and connectors and replace them, if necessary
Check the function of the main contactor and replace it, if necessary
Check power module and replace it, if necessary
Check emergency stop 7S1 and replace it, it necessary
Check key switch S1 and replace it, if necessary
Check fan 9M2 or 9M3 and replace it, if necessary