Im not at all a code reader, however, it sounds like it has to do with the second group of injector wires (the ones closest to the firewall 4,5,6). If you look on the right side of the valve cover (if your facing the truck), there are 2 different plugs with 6 or so wires in each. One plug is about where your intake manifold is, and the other is about halfway back on the fuel rail. When your reader said "injector group B", I would assume its referring to the 2nd plug. Just thinking out loud here. Maybe check it out and see if one of ther wires are cracked or broken.
Tuned by H&S, Air by Forced Inductions, Fuel by Floor-It, Goerend and SC illegitimate child 47re
Special thanks to Dave, Aron, Ashley and James
Before Dave's MCC 8.11 @83.4 1/8mi
After Dave's MCC 7.80 @87.4 1/8mi