Hi, I own a 2000 GMC Sierra 1500 SLE Ext. Cab. My question is why does my ABS and Parking Brake Light turn on after sometimes driving on a really bumpy road or just after driving on a solid road for about 30 mins. I got new rotors and pads about maybe 2-3 months ago. My tires are pretty worn out but there getting replaced in less then month and I just got my alignment done about 1 month ago.