How to fix hardware errors on R640

The server began to shut down frequently. After rebooting it, it works maybe for 48 hours. The errors are

Error Code: 2000-0251

Validation: 98786

Critical. CPU2 VCCIO PG: Voltage sensor for CPU2, state asserted was asserted

Critical: System Board Pfalut Fail Safe: Voltage sensor for System Board, state asserted was asserted

 

The other symptoms I found is that iDRAC port sometimes does not light up and disconnected with unknown reason.

The two power units are firmly connected to the server.

Are there any parts I just buy and replace to fix this?

Any advice is appreciated. Thank you very much.