Cylinder head rebuild DD15 now CPC not communicating

Hello,

I was having issues with my 2016 Freightliner Cascadia DD15 engine was hydrolocking found out cylinder head was cracked and coolant was leaking into it. Got it replaced and rebuilt. Truck starts and runs but I keep getting the following codes:

SPN 3509 FMI 4
SPN 3563 FMI 10

and the engine RPM keeps going up and down while idling.

The mechanic says he hooked up the computer and the only issue he’s seeing is the CPC isn’t communicating with the truck and that it might be bad or need to be reflashed since the truck with sitting disconnected without battery for a long time (4 weeks).

He is saying he will get the CPC checked from the dealer to see if it’s bad or if it just needs to be reflashed. I didn’t have this problem prior to bringing the truck to him.

Anyone have any idea what might be going on?

He also replaced the HP fuel pump and replaced the DPF filters since they needed cleaning.