Dodge Repair Questions? Ask a Mechanic for Answers ASAP
If there are no trouble codes present, the symptom you describe could be caused by a restricted fuel filter. You might have gotten a bad batch of fuel at your last stop. Change the fuel filter and look for water or algae in the canister. Disconnect the fuel line that comes from the tank and blow backward toward the tank to clear any blockage at the pickup.You say it has no power over 2000 RPM; does it pull hard on grades at just below 2000? Will it only rev to 2000 even in neutral? In other words is it a load based problem or and RPM problem? Load based probably means fuel delivery.
Sounds like it's starving for fuel under load. There should not be anything but clean diesel in that filter housing. I would start by thoroughly cleaning that housing and installing a fresh new filter. If you suspect what's currently in the tank is contaminated, you might want to rig a temporary supply tank for testing purposes.
By any chance, do you have access to a scan tool that can read data such as fuel pressures, etc.?
No codes is an indication that there are no faults with the system, which makes me believe it is indeed a fuel supply issue.