i had the same message pop up and it pissed me off because of all the problems i have been having with this thing. Shut down the car to see if it would reset and it didn't, so i thought for sure i would have to take it in. The next day it didn't show up and i called the dealer and they said all they could do is to see if it stored a code, well of course i might as well buy a new car for as much as that would be. So i let it go i think it was because of the cold it was one of the first days at 10- F so thats what im thinking it was with mine. These things have crappy electrical systems my climate control some time will not work when its really cold the fan will stay on low when its on high. Not sure if i will ever buy GM again should have stayed with ford.

A lot of strange 'gremlins' come into play when the outside temp gets down way below zero degrees,.....on my '00 SSEi[this is the first Winter that I have owned/driven my car in],when I locked/unlocked the car with the key-fob,a 'service car locking system'came up on the DIC(I shut off the car and restarted it and the message went away[could have been the solenoid/sensor in the gas flow shut-off unit was partially frozen,....or a door/trunk solenoid/fuel filler door solenoid frozen???]),.......also,in other frozen temperature problems, the wheel speed sensors could have slush-turned-to-ice on them,causing a code/messege on DIC to pop up,......or in the self-levelling air shocks system the mechanical lever/sensor(located on the drivers side rear shock/frame assembly,like Pontiac Dad mentioned,could be frozen and/or electrically disconnected in some way(a LOT of slush and ice gets kicked up in that area during Winter driving).
Regards,Bill

Any moisture will expand when frozen and help to push the connector loose, as well the the cold makes the wire britle and suspect to damage.