check engine light

[gary pichon]

On my way from Atlanta to Memphis the check engine light came on . The car continued to run fine. I took it to the BMW dealer who had his tech scan the car and he replaced the O2 sensor before the converter for $288.00. After about 200 miles of driving the check engine light came on again.

This time I took it to my local mechanic who did a generic OBDII scan and told me the code was for a bad or loose gas cap. We checked the gas cap and nothing appeared wrong. He cleared the light and it has not come on again after driving about 20 miles.

Did the tech at the BMW dealer blow it? Could these problems be related ? Anyone had this problem with a gas cap and should it be replaced? When an O2 sensor malfunctions what are the normal symptoms.

Thanks Gary

 

[Stone]

On my way from Atlanta to Memphis the check engine light came on . The car continued to run fine. I took it to the BMW dealer who had his tech scan the car and he replaced the O2 sensor before the converter for $288.00. After about 200 miles of driving the check engine light came on again.

This time I took it to my local mechanic who did a generic OBDII scan and told me the code was for a bad or loose gas cap. We checked the gas cap and nothing appeared wrong. He cleared the light and it has not come on again after driving about 20 miles.

Did the tech at the BMW dealer blow it? Could these problems be related ? Anyone had this problem with a gas cap and should it be replaced? When an O2 sensor malfunctions what are the normal symptoms.

Thanks Gary

Gary,

I realize my post comes 2 months too late (you had no responses), but here's my input: Buy a Scan/Reset Tool (the appropriate Peake R5 for BMW) for about $100. At least you will have an idea of the problem before you go to a dealership. I don't think you can reset "Engine Light" if there is a real "fault".

Good Luck!

 

[Bear6360]

Yeah Gary....sorry I'm late too.
I just had my O2 sensor replaced last week. It ran me $228. The sensor was $146 (the pre cat).

...as for the gas cap, I doubt it was related to the O2 sensor.

 

[bmwz3]

The gas cap thing can make the check engine light go off. This happend to my VW and my Z3. My little 95 pound wife was complaining about it being to tight so I just put on there loosely.
The light came on and nothing was wrong (something about back pressure they said). So they said to give the cap 5 good clicks. My wife will just have to get some musscles.

 

[Big Daddy]

Yes a loose cap will cause the "check engine" failure, but I agree with Bear, I do not think it will affect the 02 sensor so that a replacement would be required.

 

[Zee3Coupe]

This might be a dead thread by now, but an O2 sensor problem is driving me nuts. My Service Engine Soon light came on recently in my '00 Z3 2.8 coupe, and my mechanic diagnosed it as a "no signal" from one of the two front O2 sensors. He diagnosed the same problem on the car a while ago, and suggested we replace both pre-cat sensors (about $500 combined). I scheduled an appointment for next week.

Well, yesterday the Service Engine Soon light went off, and hasn't come back on. The bulb is not dead because it comes on briefly when you turn the ignition to on, but my understanding is that once its been tripped, it stays on until its been reset.

Any thoughts on this? Why would there be no signal from the O2 sensor (unless its a wiring problem, shouldn't an 'O2' light go on?) How and why would it reset itself, and if it is an O2 sensor problem, how come it hasn't come back on? And why would I have to replace both of them? I trust my mechanic and the guy does great work, but I'm having a hard time understanding this one....

 

[Thief]

The dealership did warn me that not giving the gas cap a few extra clicks will bring on the engine light, they also said that I would have to bring it to the dealership to get it wiped?? Is that true?? If so I will always have to put gas, and can never use full serve again, no way I can trust the attendant to make those clicks.

Thanks in advance
Thief