What would cause my 2016 Toyota Camry gas cap check engine light to come on?

If Your 2016 Toyota Camry has a check engine light that turns on at the dash then the first thing You should do is try to get off the road as soon as possible to prevent damage to Your engine. Once You are stopped You can use an OBD II scan tool to read the codes in the ECU that were thrown. One of the most common reasons a check engine light will turn on is when there is a loose gas cap. A loose gas cap can lead to a massive vacuum leak that will be detected. You should make sure the cap is tight, and if it is then You may need to replace it with a new one since they can wear out.