On the 04 it is showing a P0088. Says fuel rail/system pressure-too high. The next code is a: P0251 injection pump fuel metering control A(cam/rotor/injector). Any ideas on what these error codes represent? What do we need to do to get these cleared out of the system? Thanks for your help in advance.

My first guess would be that the FCA is failing, and allowing for too much rail pressure.

My first guess would be that the FCA is failing, and allowing for too much rail pressure.[/QUOT

What is the FCA i'm not sure what it is?

fuel control actuator.

Yep, its what meters the fuel to be pressurized. If its failing and allowing too much fuel in then you get too much pressure.It's located on the back of the CP3, and it has the only electrical connection on the CP3 attached to it. I am not aware of any real ways to test it. I hear if you shake it and it rattles its good?? But I am not sure I trust that..

fuel control actuator.

Were is the fuel control actuator located on the truck?

Back of the CP3, which on your 04 is under the APPS on the driver side of the motor.

I replaced the the FCA and fixed the problem, thanks to everybody for giveing me the useful input!!

Shoot if I was paying attention... I would been able to point you to... http://mopar.mopar1973man.com/cummins/3rdgen/fca/fca.htm

Good deal!