I'm not familiar with this truck model , the code would sugest that the power system is an EV - 100 system, and you may have a malfunction of the direction contacts, check them for slow operation and possible welding,

The code would sugest that voltage at T2 main power terminal is less than 12% of battery voltage you should check D3 diode for short circuit or the suppressor that is mounted across it.

Regards Titus