what could be wrong when the check engine light is on?
There are many reasons for your check engine light to be on. Have your computer scanned & post the trouble code(s) here so we can help. Many auto parts stores like Advance & Auto Zone will do it for free. HTH. -Jim
There are around 1,000 trouble codes. Any one of them can turn the light on. http://www.obd-codes.com/trouble_codes/
Long shot but make sure gas cap is snug.
Search Toyota RAV4 Questions
Toyota RAV4 Experts