That code will not cause you to fail an emissions test as long as they are able to command the SES light on and off properly. Does it say the code is Current or History? If it's history, clear it before you get your emissions test and see if it comes back.
Have you ever had any problems with the dashboard instruments or display? Any weird error messages or behavior in the past? The code basically means that the computer was unable to talk to the Dash Integration Module at some point in the past or in the present. (history or current) If everything seems to be working OK and the code is History, it's probably nothing to worry about. If you start experiencing strange electrical or dashboard behavior, it's probably worth having it checked out. For now, go get your emissions test and don't worry about it.
Hope that helps... Good luck! Let us know what you do and how it turns out.
Thanks, The code was a history code. I just cleared it and will see if it comes back. I have only had the 99 STS for about a year now and don't remember anything funny going on with the dash. Thanks again I will take car in next to get the e-check!!