2002 5.3 DBW issues

[t-tung]

Got a few issues. Using a PSI harness and PSI brake switch. Engine fires and idles fine. It will rev fine with the foot off the brake but not with the brake pedal depressed. Like if I wanted to do a power brake, I wouldn't be able to. That is the minor problem but I think it may be tied to the big problem. I hooked up a Snap-On scanner to it and I'm not getting any voltage readings in the TAC data screen and its throwing a P0122 code. We verified all 3 5-volt signals going into the TAC from the pedal (2 0-5 when depressing pedal and 1 5-0 when depressing pedal.) So the pedal is working. We checked the 6-wire TPS on the throttle body; all checked out fine. Check the 2-wire connector (brown in A; yellow in B) throttle body connector. It works. I'm not sure what else to look at. Seems like there's something out of place between the TAC and the PCM. On the scanner when looking at engine data, it shows when you depress and release the brake pedal. Doesn't show up on the TAC data screen. I don't know if there's something that I'VE got wired wrong or if maybe one of the wires between the TAC and the PCM are in the wrong spot.
I've tried another pedal and TAC module from an 03 and have seen no difference.

What am I missing here??