Abs Issue

[danabike]

I've got an ABS light issue. I checked the ABS codes and got a code 63 using a jumper from A to H at the diagnostic port. When the key is turned on, there is a cycling of what sounds like a servo or pump, and then the codes flash. Is the cycling a normal part of a diagnostic and what is an ABS code 63? I'll keep scouring the forum, but a little help would be appreciated.

 

OK, I did a little more digging and found that it might be a rear ABS sensor low signal or no signal. From what I have gleaned so far, the rear doesn't have a separate sensor input as the front wheels do. Where are the rear sensors located? Same as the front? I normally work on imports, but just picked up this Suburban for a song. It's a 93 2WD with a 350 and automatic tranny. The ABS light and the brake light both stay on.. No engine codes other than diagnostic mode code 12, and ABS code 63. Leaning more every minute!