Braking Vibration in 04 CTS
 

Hi everyone. I have an 04 CTS, that sat for about 3 months. Now that I am driving it again, I am noticing that I have a horrible vibration when I am braking. Its definitely coming from the rear. At first I was thinking rear pads and rotors, until I really paid attention..I just barely apply the brakes and I still get the vibration..if I have them on, it feels like the ABS is activating, and the tires may lock up a little, possible ABS issue? I have no lights on or codes being thrown. It just feels like more than warped rotors. Any ideas??