2004 Volvo S40 engine whining + eng light on

Can you have the codes read off and post them on here?

The noise you hear could be related to the code and possibly your oil leak. The PCV box or oil trap box as some may call them, has a diaphram inside that teasr and creats an internal vacuum leak that starts to make a whistling sound. That box usually leaks engine oil as well. Quick way to test this is to remove the oil dipstick. Once you do you will hear a load suction noise and the whistling will stop. If you are in the United States especially in California, the oil trap is covered under an extended warranty of 10 years/150k miles. You would need to call Volvo to verify this by giving them your VIN#. You may also want to look in to upgrading the ECM software as well if one is available and is also covered by the same extended warranty. Good luck and hope this information helps you.

I am glad the information was helpfull. And yes, removing the oil cap would also give you the same results. If it is not covered under warranty then at least you know now it is the oil trap box that is making the noise. If you do the repair yourself, make sure you reset the fuel trim adaptations or the fuel trim code will return. Usually unplugging the ecm will do that. Well keep me posted.

I am glad it worked out for you and that they did cover under warranty. Thanks for the vote :)