Oxygen Sensor light is on, what to do

Post your E12 technical questions and comments here. Please, no off-topic posts.

Moderators: Mike W., Pierre

Post Reply
brotherhay
Posts: 66
Joined: Fri Apr 17, 2009 11:40 am

Oxygen Sensor light is on, what to do

Post by brotherhay »

First post since the new board has come around. I used to go by Michael-WI on the old BB, but now this board is live, its Brotherhay!

To reiterate what I have is a 1980 528i. Ive owned this car for many years, and have put alot of cash into it. Well, as of a few years ago (this car only comes out in summer), I have had the O2 sensor light on. I have gone though alot of issues, hard starting, high idle, things like this. As of last night a new O2 sensor was installed, and the throttle body adjustment in the FAQ section was done. Seems like the car is a bit snappier, and idles at 800rpm, which is better. But, 02 sensor still on.

Is this just something that needs to be reset?

Also, a little off topic maybe. I did see a diagnostic peice that you connected to the connector in the fuse box a long time ago on Bavauto, but now I dont see that. If those things are worth it, maybe its time to invest in that to help trouble shoot.
User avatar
Mike W.
Posts: 2790
Joined: Wed Aug 30, 2006 12:12 am
Location: Sonoma County

Post by Mike W. »

This is an easy one. There is a counter box mounted on the frame, somewhere down by the steering box. It has two buttons on it. Push both of them, twice, to reset it. It's solely a mechanical counter stuck in the middle of the speedometer cable and is supposed to go off at about a 25K interval. But it sounds like you were due to an O2 sensor anyway. You've got to crawl under the car, but it's an easy no cost fix, the best kind! :lol:
Mike W.



1980 528i, 3.5 euro, 5 speed conversion
1981 528i, 3.6, Recaros and more. Project
1998 328is, quick and efficient, but not satisfying
2000 528iit, Vacation mobile/wife's grocery getter
brotherhay
Posts: 66
Joined: Fri Apr 17, 2009 11:40 am

Post by brotherhay »

I suspect you mean the box that the speedometer cable goes to?

I will get under that today, does sound easy.
T.Hanson
Posts: 1696
Joined: Wed Jul 26, 2006 7:39 am

Post by T.Hanson »

Yes, that's the box.

For all the other gremlins, first check all brown wire connections clean. In the engine bay, under the dash. Same for braided strap(s) engine to firewall, negative battery post.

If you did the throttle body adjusto, the off throttle switch should click the lever at the last possible moment. If it clicks the lever sooner it cuts the fuel off and makes the throttle pedal jerky. Called trailer hitching.

Do the timing FAQ. Super deal is new rotor, cap, plugs ( Bosch WR 9 DS, S for Silber.) Wires if old. That is the starting place for setting the idle, bypass screw on the throttle body.

Where the gas pedal arm, lever up from the toe, gets hinged in the firewall, there are two rubber bushings. About the size of a quarter. Good if they are good. If not, new ones make the throttle response, linkage, way incredible fantastic new.
Post Reply