You are correct, the wire from the brakes to the "PCM" is purple. There is no wire from the brakes to the trans on a `96 B-body. The 12v power for the TCC solenoids, there are two, comes from the emissions fuse and supplies power to the entire trans along with the O2's, MAF, AIR pump relay, EGR and EVAP solenoids. The ground side as usual comes from the PCM.