There is no way to read the codes without a scanner. Some codes will clear if you disconnect the batteries for 15-20 minutes, but if the problem is still there, it will go "Limp" again.
Drive to an auto parts store and have them check the codes-- write them down before they are cleared. (Some places will only read codes-- not erase them, because of liability)
Might be time to purchase a code reader, then you would be able to read, and clear codes yourself.
Chevy 04.5 LLY, 2X, shell, XDR, MikeL Heavy duty up-grade, 6spd, TransGo, deep pan, de-badged, 65 Gallon replacement Aero tank, LBZ-mp, Kennedy pump, shimmed, Pre-fuel filter, tow mirrors, BU cam, gauges, GPS, Sirius, bags, custom grille, fender vents, HD trans cooler- Curt front hitch, footwell lights, load lights, Studs, head gaskets.