I have contacted GM for this same issue. Today's response was that the warranty was out, plus I was the second owner, so they weren't going to fix it. I drive 3000 miles plus every month, and have proof of steering problems prior to the 150K miles that they shut off at. I found the service bulletin at 151,386. This will be the last GM product that I will ever buy, and I've been a GM owner/driver for 35 years.
They want to bug the crap ought of me for a liftgate recall, and the fact that I haven't taken it in yet for that repair, but can't notify me of the steering issue? I've narrowly avoided wrecks, thanks to this, several times were way too close for comfort.