Freightliner Century Detroit 60 turns won't start

I have an RV that started life as a 2001 Freightliner Century last four of VIN 9796. It has a Detroit 60 series. Other than the RV conversion in back the front is all stock Freightliner.

The engine turns but won't start. While cranking I get the red engine prot light flashing and when I stop cranking the dash says low voltage. I checked the codes and it flashed me red 25 and yellow check engine 24, 22, and 77. We can't get a real scanner on it until next week.

So far we have tried:

New battery
Jumping with boost charger and new battery
Squirting WD-40 into intake access plug

Same result, turns but no start and same messages.

Any ideas on what to try next?

Thanks