Do it yourself, replace the spark plugs on your Hyundai Sonata produced in the years 2009, 2010, 2011, 2012, 2013 and 2014. For this particular task you will need four new spark plugs from the auto parts shop, a 10 mm socket wrench and a spark plug socket wrench. The repair is fairly easy and it will take you about 20 minutes.
First of all, go to the battery and unplug the negative cable, in order to avoid errors on the computer or unwanted shortcuts. Then, you should remove the engine cover to get access to the ignition coils and beneath them, to the spark plugs (see image below).
After you locate the four coils, you will have to unscrew the 10 mm bolts that hold them (see their position marked with red arrows in the next image). If it helps, you can disconnect the harnesses (see the blue arrows in the picture below).
Now, unplug the ignition coils and, using a 5/8 spark plug socket wrench with an extension, remove the old spark plugs (see the next picture).
In the final step, install the new spark plugs. Install the coils back, connect their harnesses if you removed them and tighten the four screws. At the end, remember to plug back the negative cable of the battery. This is all you have to do if you need to replace the spark plugs on your Hyundai Sonata manufactured between the years 2009 and 2014.