my steering wheel shook very bad, especially when going down a hill. also the the brakes get a pulsating feeling in the peddle. no my service traction control light and service abs light is on. so they said i needed all 4 rotors replaced, a full wheel alignment and brake pads. i had all this done now they say i need speed sensors??? this car is a 2007 grand prix and only has 43,000 miles. ive never had a car require this much repair in this period of time. why does this happen? and all 4 rotors at the same time? and what are speed sensors? it cost me 665.00 dollars so far and am looking at another 400 for speed sensors and installation. i dont really have any idea about this and dont want to get taken. thank you to anyone that can help answer my questions.