What would cause my 2010 Ford Fusion Hybrid check engine light to come on?

There are a number of different reasons why a check engine light would come on in any vehicle, and that extends to You 2010 Ford Fusion Hybrid. Essentially, the check engine light is a catch all for many issues that relate to the engine, electrical system, transmission, and others; You'll need to check the diagnostic trouble codes (DTCs) that Your Fusion is giving You with an OBD-II scan tool. Some of the most common reasons are an EVAP emissions leak (from a loose gas cap to a failed purge canister), bad spark plugs, a faulty thermostat, defective oxygen sensors, or a malfunctioning engine control module. The causes really run the gamut, so it's important that You begin narrowing Your issues down with the codes as soon as possible -- since some of the issues may be quite severe.