GMC Repair: brake noise, safari van, little buzz

Question
Hi I have a 2003 safari van that developed a weird problem with the anti-lock brake system.
When I apply the brakes, all works fine until the van is almost at a stand still , then I hear a little buzz from the front ( could be the left wheel) and the brake gets a little spongy until the van stops. No problem stopping .
no warning lights come on .
Any idea what part could cause it? Thanks

Answer
Dear Jurgen,

That's a new one for me.  I guess there's always something we haven't seen before.  If the problem only happens going really slow, I would suspect some dirt or leaves are stuck in the antilock sensor vanes on the hub, making the computer think the wheel is going slower than it really is, or maybe there's some grease and dirt built up and stuck between some of the little vanes so the sensor sends back a false reading to the computer.  That's all I would know to check on this one, but it could be accurate.

Thanks so much for choosing me, and best of luck to you with this.  I love those vans, I hope you enjoy yours!