Tonight on the way home from work just happened to look at the info screen and saw a service power steering system message, it went away just as quick as I saw it. Hit the OnStar button for a system check, turned up nothing since no service light was on, call ended a minute later the message came back with the warning light in the rpm gauge then went out in 15 seconds, no idea what is wrong fluid checked and is good, only have 14k on it, any ideas