You need to take it to someone who can scan the car for codes. A shop wants about $70 for this, but here, Auto Zone will do it for free, in hopes you will buy whatever you need from them. But be careful! An engine might give you a code for an o2 sensor, but that doesnt mean you need an o2 sensor. Manny different things lead to a code, It's not always a bad part. Get a second opinion after you know what the scan reviles.