I also have a 99 with 131k on it and my ses light came on as well. It has come on a few times and has been reset. From what I can tell you will need a scan reader. A few here on the board recommend a autoengunity brand. If you are a do it yorselfer and like to stay out of the dealerships a scanner is a must have. Then do a search on this boar for the scanned code number, then Fix or repaur daily.