I would pick up a cheap used Superchips 1705 programmer for the PSD, not for the tunes but for the code reading. Before you just start replacing parts check the ABS lines where they plug into the back of the hubs!! One may be loose. Is yours 4 wheel ABS or two? And it is correct because of the GVWR of our trucks were aren't OBD II compliant so the scanners at the auto parts stores won't work.
NCH