2005 Mitsubishi Fuso FE 180

These codes came up. Anybody know what I should be looking for. The motor has 225k
I’ve worked on regular gas engines this is my first with diesel. I changed the fuel filter housing. Reconnected the muffler with a new engine pipe. New thermostat. New air filter. On warm up very little power. Then it seems to have decent power. It was overheating. Changed the thermostat and it appears ok so far I will replace the radiator cap. The truck sat for 2 years before being driven. After I purchased it and did some restoration I drove it 150 mile to its present location in the mountains of Massachusetts. I’m taking it to Tucson within the next several months. That’s where I’m moving. Any direction would be greatly appreciated
PO254
335
381
404
251
P 1635
P1630

Hello

Welcome to TDP

The P0254 is possibly as simple as a dirty fuel filter.....

With all the codes listed I would do the following.

Clean the battery terminals and make sure the battery/batteries are well charged.

Changed the fuel filter/s and purge/bleed the air from the system per the manufactures recommendations.

Grab a scan tool and clear all the codes.....

Run the engine and drive the rig......see what if any codes come back.

With so many codes it is not wise to start "Chasing the Wind" so to speak and tossing time and money at things until you get a real handle on what is really happening.

Good luck....