I have a 2007 sts....started to get "service steering system" message. was getting harder to turn steering wheel. fluid was good. I took it to garage and they told me it was a faulty sensor wire that tells the rack/pinion to either tighten or loosen the steering depending if you are city or highway driving. they replaced the wire and worked fine on the way back from garage. I just want to see if anyone has heard of this.