2003 Aztek brake problem

My brakes make a bumping noise at low speed braking. Sometimes the anti-lock brake light comes on. Can’t seem to find the source of the problem.

The bumping noise is probably the ABS kicking in abnormally. The ABS light coming on makes that a really easy guess.

Usually, when the ABS stops functioning, the regular brakes work just fine. That may not be the case here (you didn’t mention whether the bumping occurs only on slippery surfaces). You need to take it to a shop that has the proper scan tool for reading codes from the ABS controller. Pronto.