Dumb question for me, I am only on my second cup of coffee.
Did you check the battery junction box fuse # 11 ?
The posts above are talking about an inline on the 1997 MY truck, which is this
Your MY truck is a 2002, and there were quite a few changed from the 97-98 MY range.
This is a 2000 MY EVTM page, but you can see the similar fuse is now in the Battery Junction Box ( aka BJB or engine compartment fuse panel )
The BJB fuse #11 feeds the regulator, and regulator field.
One of the output of the regulator feeds the charge indicator on the instrument cluster, which the other side of that circuit is Central Junction Box ( aka CJB, passenger compartment fuse panel ) 30, 30 A fuse.
Check those 2 fuses if you really are having the same charging problems.
If they are blown, it could have been a one time thing, or it could be a problem with the regulator on the generator.
Without the fuse links, the battery would be isolated, and the truck would not even start.
Also as Bluejay posted, check the connections on both sides of the battery, and the other end of each cable. Check for frayed cable at the ring terminal.