First of all, the ABS is a system designed to prevent brakes from locking up. That loud pulsing noise you hear is the ABS rapidly applying and releasing your brakes to maximum efficiency. It is normal. You should also stop efficiently though.
If you are used to non ABS brakes it can seem as though you are not stopping as quickly. The rapid fire noise is a good thing and means the brakes are working correctly.
If your brakes are locking up you have a problem that would almost certainly show up on a code scan. Have you had a mechanic drive the car and experience the problem you are having?
April, 14, 2011 AT 1:50 AM
You have a wheel speed sensor dropping out at low speeds, the EBCM see's this as a locked up wheel, thus activating ABS, very common problem with GM's trucks and suv's, rust builds up under sensor increasing the air gap between the sensor and tone ring, will rarely set a code because to the EBCM, the system is working normal.