Need Diagnostic Help

Ok guys, my '94 threw a CEL the other day for the first time ever. Pulled the PCM flasher codes off the dash and got 12, 41, and 37. Only getting 12.6V when running so it seems like the alternator isn't charging but the question is why? Is it a bad alternator or is the PCM not telling the alternator to charge?



Truck Details:

-1994 Dodge Ram 2500 4x4

-241,000 miles

-Automatic

-12V

-10 plate, intake, and exhaust