OK, I've had my new old '87 GL wagon for a couple weeks now, passed CA smog (easily), it seems to run great, why is my "check engine" light coming on? I've never owned a "modern" car, and I gather that this is due to one of the smog sensors spitting out a code that can be downloaded with the proper tool. I really enjoy the way the car handles and I've been pitching it around on the twisty bits -- could this be a cause? Sloshing gas into an overflow or something? (yes, the gas cap it on tight)....BTW, you all probably have seen this, but I found it interesting: http://subaru.sonik.us/vindecode.html. Thanks in advance for any feedback!

Your car's computer has an LED embedded on the front that will flash different codes depending on what has failed. You can check the Ultimate Subaru Repair Manual for more information.

This link gives you details on how to do this:

 

http://www.ultimatesubaru.org/USRM2/mick-usrm/electrical/ecucodes.html