Mine started doing that the same day I bought it... Only on the highway with the a/c on. I called the garage and they said that when they shampoo the engine, it screws the sensors... they said to reset the computer by disconecting the battery for a few seconds. It did the trick, the light never flashed again.
Try resetting your computer, if your light comes up again after that, you do have a problem with your engine... could be anything... go to mazda, they'll do a diagnostic... It's probably a sensor malfunctionning...
Hope It's nothing!

good luck!