Collision Avoidance comprised of Following Gap and Alarm / Auto Braking ds not function. One dealer after two trips and unable to repair stated that GM is working on a new software update and until that is available repair is not possible. No date was provided by dealer or GM customer service as to when this update would be available. Second dealer stated that system was in fact not functioning, and asked me to return in a couple days, so he could research the issue, He knew nothing about a pending update. Both dealers stated that no alarms or codes were present in spite of failure.