ABS light on but no code (97 Bravada)

My ABS light has been going on and off for about a week now. It comes on while I am driving and stays on but if I turn the car (http://www.automotiveforums.com/vbulletin/#) off and back on, it goes off but comes on again while I am driving. The ABS system has even activated a few times when I was stopping on dry pavement. I took it to a shop down the street and he put his ABS (http://www.automotiveforums.com/vbulletin/#) scanner on it and no codes were found. So he used another scanner and no codes showed up even though the light was on.
I replaced both front wheel bearings about 2 months ago and they came with new speed sensors.
Any ideas??
Today the ABS system kicked in wen I applied the brake and the ABS light never came on.

Check your connections at the wheels for the ABS. A poor or bad connection will usually cause this. Unplug the connector bend the metal tabs inside a little and reconnect it, for a better connection.

Use CRC electric cleaner + dielectric grease on connectors.

The ABS does a self test each time the vehicle is started, when the vehicle is moved at approx 5 mph, the wheel speed sensors are checked and the module completes the self test. If the orange ABS light comes on, a code is set in memory. The code will remain in memory until the ignition is shut off, then it is cleared. This is probably why your tech can't find any codes in memory.

Very common problem. This should help with diagnosis & repair:

http://ww2.justanswer.com/uploads/heavychevy396/2010-04-17_150656_2000_Chevrolet_Blazer_abs_coming_on.pdf