Check Engine Light

[TJ_ti]

Ok I am looking at a ti that has a BPM intake and a new cat with a modified Arsa(?) M3 exhuast to fit, he says that the Check Engine Light (CEL) comes on some times if it is driven hard but if you just drive normal it turns on. Any clue what that could be, he was thinking that maybe it was the MAP sensor, and i was wondering if there is supposed to be another O2 sensor somewhere that is not on the new cat or exhuast. Please let me know what you find out.

[1996 328ti]

I'd suggest reading the code after the CEL goes on and not guess. Maybe some in your area has a code reader you can borrow.

[Jeff Spooner]

TJ
When asking for help please give the year model. The only way to know what code the cel is on for is to read the DME with the proper tool. We do not have ESP for BMW's downloaded yet. the aftermarket parts installed are not always the reasons for the CEL on. If the light comes on the code is stored in the DME, you do not have to check it with the light on. Take it to a good BMW shop and they can tell you why the light is on.

[TJ_ti]

Oh sorry it is a 1998. Yeah I am trying to diagnois this probelm my self, I am more of a hands on learn what I can kind of guy. Thanks for the help keep the suggestions coming.

[ZeroG]

Oh sorry it is a 1998. Yeah I am trying to diagnois this probelm my self, I am more of a hands on learn what I can kind of guy. Thanks for the help keep the suggestions coming.

When it is driven hard and comes on it could be because the amount of air that is passing through the MAF sensor is exceding the 5V that the ecu can handle. This is probably due to the intake.

BMW's do no have a MAP sensor they use MAF or AFM. As for it coming on when you are just driving around it is probably an O2 sensor. But they're all right that you really need a code reader to know for sure.

-Chad

[robcarync]

i may guess o2 sensor as well but i dont know much about cars...i just know my o2 sensor went out...and the CEL only came on occasionally like you said.

id sitll suggest a code reader so you know for sure...youd hate to put work into the car and then have replaced the worng part.

someone im sure will correct me but i think a 98 has 2 o2 sensors but again i dont know for sure

[TJ_ti]

This is what I am thinking. I was just making sure well I am waiting to get it so I will let you know what it is when it gets here. Keep the suggestions coming though.

[robcarync]

also since you have 2 o2 sensors...it would be another reason to get the code reader so you know which one to replace (or you may want to replace both...not sure but it seems logical that if one goes out, the other one wont be far behind)

either way, if it in deed turns up to be the o2 sensor, they are really easy to replace and can be done fairly quickly

[TJ_ti]

Well thanks guys I appreciate the help, yeah I am pretty mechanically inclined person and actually have had to change the O2 sensor on and old Prelude that I used to have. I will let you guys know what I find out I get to pick it up this weekend I hope.

[aceyx]

ti's with M44 motors will have 2 oxygen sensors, thanks to ODBII (i hate the EPA). the one up front is easy to change. pop the hood, change it up. the one underneath . . . not so much fun. try and do it when your car is nice and cool.