I have the same problem. First thing to do is get the code read. I hear many chain-type auto parts stores such as Advance Auto Parts will do this for free in the parking lot. Personally, I bought a device from Digimoto.com for ~$100.00 (price of one trip to the dealer) that interfaces the car to a laptop so I could read and reset the the code as many times as I want. It's great for peace of mind, because you can find out for yourself what's going on.

Does the car run OK? If so you might have what I have - code P0410, Secondary Air Injection System Malfunction. Pretty common in these cars I hear, and tends to be intermittent. It's an emissions control thing that you can ignore pretty much, though you should get it fixed eventually. Mine started acting up several months ago. The first time, I took it to my mechanic, who cleaned the system and told me to watch it. about a month later it came on again, I took it in, he read and reset it and told me to just watch it (I like this about him - he won't do unneccessary repairs just to make a buck). The third time, I got curious and bought the code reader. I've read and reset it a couple of times since then, and it's always the same P0410. Someday I'll get it fixed...

Then again, there are lots of codes, and you could have any one of them...

If you just want to turn off the light, try this: Disconnect the battery for several minutes, then reconnect it. If the fault is only intermittent, the light should stay off until the fault happens again. But be sure to have your radio code handy if you do this.

Good luck!