1995 Gmc Suburban Abs Problem

Hi everyone-

I have a 1995 GMC Suburban 1500 w/ABS and 4WD. When I deccelerate to a red light the brakes work just fine until I reach 10 MPH-at which time the ABS pump kicks in for about 5 seconds. It's only when I reach 10MPH that it does this. When driving on the highway I can brake all I want with no ABS issue. Anyone ever experienced this?

i have just purchased this vehicle so i'm still learning whats wrong with this one so here is my take on the problem.
the system works thru a large box under the hood with about 8 brake lines going into and coming out of it. the system cam be checked by a dealer on there computer diagnostic system. you can also do a self diagnostic on the 3c system (computer control system) with a paper clip. if you have a manual for the truck it will tell you how to do this.