2020 Ram Longhorn over charging

[Booner92]

Hello, my brother recently bought a wrecked longhorn. He had to replace the dash as the airbags went off.. after fixing most of the body work and putting a new dash in everything works except the charging system. When you start it up it runs fun then maybe 30 seconds later it way over charges and everything shuts down electronically “engine still runs” it goes up to 17v

Replaced a battery and the alternator and hasn’t fixed it. It definitely seems like it’s not reading the voltage right on the battery therefore it’s overcharging. Any thoughts would be appreciated only thing we can think of now is the PCM is messed up but not sure