07 Volvo D12 flicking gauges truck shutdown

Hello I have an 2007 Volvo 630 D12 motor. It's giving me problems with the instrument gauges turning off and on, and acting crazy. Once the gauges start acting up it will also do it on idle. Also when the gauges act up the truck cuts out sometimes. The truck drives fine for about 10 miles then starts acting up.
The codes it that are coming up are. Sid 231 fmi 2 , psid 201 fmi 9 , sid 146 fmi 13, Ppid 119 fmi 9.
I have cleaned battery connections. All the grounds engine block, frame rail, alt, fire wall drivers side. No luck.

With the computer hooked up I can see the battery voltage going to ecm is jumpy. 13.5 to 12.8. Also when I Rev the motor up, the voltage goes down.

Any ideas where to go from here ?

 

Looks like someone deleted the fuse on the battery positive. I got good connection to vecu. And good ground from vecu to battery ground.
Still looking.

 

UPDATE
Installed a new gauge cluster, recommended by a fellow member.
No more gauge flickering or truck shutting down.

 

300 from the truck wreckers