Retrieving ABS codes - 1999 Jimmy

I am attempting to diagnose an ABS light on a 1999 Jimmy. The owner reports some unwarranted ABS activity about the time the light came on. I haven't been able to verify this. But I do suspect a faulty wheel speed sensor. This is my question - Is there a way to retrieve ABS flash codes on this vehicle? I may have access to a scan tool, but would prefer using the flash code method if possible.