You cannot adjust the fuel trim on your 2003 Dodge Ram 2500. Whatever is causing bank 1 to run rich will need to be repaired in order to get the fuel trim back to normal. Checking scan data to monitor the fuel trim on bank 2 may reveal that bank 2 is also rich but not yet rich enough to set a fault code. If that is the case items affecting the fuel trim on both banks should be checked. Please see the following RepairPal article for more information - http://repairpal.com/OBD-II-Code-P0172-and-P0175.