I have a 2007 Mercedes Benz C 230. I had a friend change the rotor on the driver side, and brake pad on both front brakes. Now, the ABS light is on and will not go off. In addition, after starting and hitting the break for the first time, there is a "washboard effect" that I experience. After the first time I brake, I do not have the problem again until I restart it and again, it only happens once. Any suggestions on solving the problem and getting the light to go off? Thanks!!!