Ok Piddler,
Now that I know what you are talking about I can give you the bad news.
If it is the SLS rear raise light then it is most likely your air compressor that is starting to fail. I had my light come on a few times recently but would often reset itself if I turned the car off then back on. I too it to the dealer and found my air compressor was not giving out enough air. I think it gets dust and crap inside it and wears things out.
Mine was under warranty so they replaced the compressor.
