Super rewarding to have my Suby after salivating over them all these years. Shortly after buying my 02' WRX a few months ago, my check engine light went on, there is nothing unusual coming out of the exhaust. This happened after I swapped the aftermarket with the stock to pass smog. I have unplugged the battery and reset the ecu and after a week it came back on. Does anyone have this problem or know how to handle it?

 

What's the mileage?

 

Is the stock exhaust still on or did you put the aftermarket back on?

 

You have to get it scanned to find out what code is set. Without that code any answers you get are pure speculation.
Unfortunately Autozone does not do free scans in CA as they do in other states, so you'll need to find another place to get it checked if you don't want to pay.