Have you checked your fuses and transmission oil level?
Did your SES light come on?
For help on fuses look in your Owners Handbook or go to,
'http://home.achilles.net/~howardm/aurora/aurora.php'
Remove leading and following '
follow the Under the hood link
If your tranny oil level is O.K. then you probably have a shift solenoid problem. Do a search on this forum for "shift solenoid" for more info or have your Aurora scanned.
Oh and welcome to the forum.