engine light turns on intermitently

[YNGRVP]

For some reason my check engine light turns on intermitently when my car is going between 35-40 miles per hour, but today i noticed that it also does it when the engine is reving between 1000 and 2500 when the light comes on i also hear a loud buzzing sound coming through the speakers. does any one have aclue? Has anyone ever had this problem? I'm thinking of taking it to the stealership to see if it comes up with any diags but wanted to get some input here first. thanks for any help.

[Cary328is]

could be O2 sensor or catalytic converter. when it comes on does it stay on or does it shut off again? if it stays on all the time, your gas cap may have been loose. you have to get it reset at the dealership or at an auto service center that does bimmers

[YNGRVP]

no it doesnt stay on it comes on for a second then it shuts off by it self.

[Cary328is]

Sounds like your O2 sensor or Cat converter are going bad! You better get those checked soon!

[YNGRVP]

Ok guys here is the deal. my 325i was having the check engine light turn on at certain rpms and only while taking off. what we found out is that it was missing that housing that goes from the hood to the alternator. Due to it being over 100 degrees here in vegas, the alternator was getting all the hot air from the radiator fan. We installed the new housing from bmw and now the car runs like a champ the light has not came back on if you. I was told by the bmw dealership that housing is very important when you live in hot weather due to it providin fresh air to the alternator and it being able to put out the right amount of power. If any one has this problem in the future hope this helps. B)