引擎燈亮了indicates there is some error signal in the system.

In the recent cars, most of the engines are controlled by a computer which receives feed back signals from bounch of sensors. When one of those sensors sends an error message, your check engine light will come on. You need to find out what is the error code. You can get this error code using a scanner. Some auto parts shop such as Autozone can scan it for free, but it depends on whether they have the scanner to scan your car. For a while, Autozone don't have the scanner to scan code for Camry. Now things may changed. Your dealer definitely can scan it, but it usually cost about $50 per scan. Once you find out the error code, you can start from there.

The most common problem to cause check engin light on is the oxygen sensor problem.