Quote Originally Posted by dndeans View Post
Does anyone think that the abs control unit could be the problem?
Not likely ... but anything is possible.

ABS modules are intentionally designed to NOT degrade braking performance if the unit fails.

My best guess is that you have a bad caliper. Second choice would be the lines (solely based on post #2). Master cylendar isn't high on my probability list since it serves all 4 brakes & only 1 is affected.