Atos Prime 2004 check engine light on
 

On a Hyundai Atos Prime 2004 ( about 30000 miles ) 1.1 liter engine the check engine light turn on.
In the car there is just a little bit loss of power.
I would like to know if could be a regular maintenance problem or is a fault.
More than this i would like to know where are located the camshaft sensor and the lambda sensor and how can i check it if they are broken ( like resistance or voltage value on the connector ).


Thanks a lot.