A little help understanding DTC's terminology
 

Okay well unfortunately I have the dreaded check engine light and 4 DTC's, it came on halfway through my trip home from ND to CO truck sputtered a little here and there, would surge, and one time the key was on I had power to everything but it just had no throttle response I took it out of gear and the engine was dead all while driving, I pulled over turned the key off started right back up and off I went no further problems. I looked them up, one is for over boost, one is for high rail pressure, makes sense because I have chips and they probably threw the code. Anyway the other two I'm a little confused about, I don't know exactly what they are trying to tell me so I'm looking for help. The first is P2508 ECM/PCM Power Input Signal Hi. The second is P2121 Throttle/Pedal Pos Sens/Switch D Circ Range/Perf. Any help would be greatly appreciated here, just trying to form a game plan, and maybe dupe the wife into a "I gotta have it" deal.