What causes my 2014 chevy sonic check engine light to come on?

In the 2014 Chevrolet Sonic (and in any other vehicle), the check engine light is essentially a catchall for many different problems. These problems encompass not only the engine, but also the fuel system, the transmission, the electrical system, and a myriad of other possible causes. The first thing You should do is check for one or more OBD2 fault codes. In the case of the Sonic, the most common check engine light issue is a leak in the EVAP system, though this is far from the only cause. You might be looking at something as simple as a loose gas cap, or as involved as a failure of the purge canister. Have Your Sonic checked with a scan tool, and get back to us with what You find; this will make the diagnosis more specific as well as more fruitful.