So the wife's 08 2500 has been throwing a cel about every other day and it comes and goes, she's getting the 1451 0489 intermittently there doesn't seem to be any limp mode action but what the heck is going on? I've searched the codes but can't figure it out.

 

Egr and doc are playing games. Throttle control a circuit for the egr is 0489, and the 1451 is dpf excessive soot level.

Sounds like the truck is not doing passive regens the way it should. Check the egr valve for proper operation, preferably with a scan tool, however. If the valve is malfunctioning, turn the key to the run position, and listen carefully. You will hear the egr valve motor screaming g at you, as it tries to cycle the valve before startup. To figure out the sound, take a cordless drill, and press the trigger lightly, the sound it makes just before the Chuck starts to turn, that's what you're listening for.

Good luck