02 Trailblazer ABS
I don't know if 2000+ models are improved, but the common Chevy ABS failure was due to the front wheel speed sensors being a little out of position. So in addition to replacing your hubs/wheel bearings as needed, the fix is to remove the sensors, clean up any dirt and/or rust on the mounting surfaces, and reattach them.
You might want to pull the ABS fuse until you get this fixed, my old Lumina van used to have this problem, and it would sometimes decide the wheels had locked up and release the brakes at inopportune times. It almost made me roll through a downhill T-intersection into a busy highway once.