Autozone only reads the PCM. You need the dealer DRBII scan too to read brake codes. There are a number of things that it can be including simple ones like the brake fluid level. Do you have 4 wheel or 2 wheel ABS? Go over to the Popular Mechanics web site. Thery had a detailed article for how to troubleshoot ABS systems a few months ago.
Yeah I've been to auto zone before to use thier code scanner. the one hear has a drbII scanner. I used it to pull a code from my pcm. The light was on at the time and no info came for the abs. is there a different port. I have 4 wheel abs 99 5.9L 4x4