Yup, it's a fairly common problem that occurs when doing water crossings, splashing in puddles and/or washing the engine. Most of the time it is the o2 sensor, and it sometimes fixes itself.

Here is a link
And another

If you do a search for "engine light" you will get MANY threads to read that have diagnostic codes listed. Some say that it fixed itself after a couple days, others went to the dealer and had the o2 sensor replaced.

I personally have not had the light come on. Although I do run STP fuel injector cleaner about every 3rd oil change to keep the injectors clean. I think this also helps the o2 sensors from getting gunked up.

A side note, I don't think disconnecting the battery will reset the error code. I'd need to check the ESM but I think I recall somebody else talking about this a long time ago.