ABS light on

Need some help. I have a 95 Suburban 4X4 with 4WAL. ABS light has been on since I've owned it. I'm getting ready to sell it and wanted to fix this problem. I have jumped the diagnostic port pins and tried hooking up a Snap-On code scanner, but it won't show any codes. I'm thinking the EBCM (Electronic Brake Control Module) is bad. Anybody had similar problems?

Need some help. I have a 95 Suburban 4X4 with 4WAL. ABS light has been on since I've owned it. I'm getting ready to sell it and wanted to fix this problem. I have jumped the diagnostic port pins and tried hooking up a Snap-On code scanner, but it won't show any codes. I'm thinking the EBCM (Electronic Brake Control Module) is bad. Anybody had similar problems?
The snappy scanner will look at abs codes and can record wheel speed inputs, you can select this function on the scanner, drive it and look for sensor inputs they should be about the same for all 4 wheels, if one is dead or more than 3-5 mph different it or the wiring is a problem