check engine light
 

well here it goes, last night i was driving with about 55mph, went uphill and once i was going downhill, i took my foot of the pedal, the car was still going with about 50 and i noticed my check engine light came on briefly, once i started to slow a bit and it went off. it did happen like this before, going downhill with my foot of the pedal.

can any1 explain why this happened, does it has to do with electrical or air, any advice is appreciated, i mean is it common to happen like that.

It's an electrical issue - sounds like a connection at an 02 sensor or similar loose connection.

well i did replace the O2 sensor last summer, what do you mean loose connection or something? the o2 sensor plugs in pretty tight there.

It's a guess. If not the sensor connections, maybe the relay is intermittently faulty. Or it could be something completely different. You need to read the fault code(s) stored to find out what is wrong, using the "5 stomp method" . . .

http://www.pelicanparts.com/BMW/tech...nostics%20.htm

have u check for codes?