98 GMC Sonoma

The best approach for this type of problem is to visit a mechanic who has a scanner that can access the ABS computer and view live data during a test drive. Typically the signal will drop out from one of the wheel speed sensors and the computer will think that wheel has locked up. In response, the hydraulic control unit will reduce fluid pressure to that wheel in a misguided attempt to get that wheel back up to speed. Most often that happens to a front wheel which does the largest percentage of stopping. The live data should show which sensor has a problem, or if there is some other problem.