My '02 3500 HO 6sp threw codes also. Light came on. Came out to be Man. Avg. Pressure was higgly piggly. Pulled EZ and went to *******, they replaced the Acc Pedal Position sensor. No big deal. Had to return to get them to erase codes as this is something they don't normally do (?). I had the elbow installed and pulled it also before going in. This was about 1 year ago... ... ..... no problems since. There is a web page to read these codes but can't recall it now.
Hope this helps as Edge said their box wouldn't do this. H'mmmmm. Anyway, my APPS was bad as it had been acting up before I threw the codes but I thought it was due to my poor shifting.