Oxygen Sensor Problem- E36 OBD1

Elfer · 09-06-2006, 03:58 PM

I have a persistent problem that is keeping me from smogging my car. The CEL in the car lit up a while back and the code came back as 1221 - Oxygen Sensor. Bought the sensor from our sponsor and installed it, cleared the code, and drove the car. The CEL is back with the same code, and it is intermittent. The CEL would come on and off, but off most of the time. It would come on for a few seconds and would go away. For SMOG purposes, the car will not pass because the code exists in the car's memory bank. Does anyone have any idea on how to properly diagnose and hopefully address this issue? The car is a 1992 325i. Thanks in advance.

Wayne 962 · Wayne 962's Garage

Firstly, you can do what I've done before - drive the car to the smog station, and clear the lamp right before you get there. Then see if it will pass smog (the light will usually not go on right away). I've done this with my truck and a faulty EGR system that I never did fix. This will at least get you driving again.

As for the 02 code popping, if you've replaced the sensor, then I would suspect the wiring harness to the sensor. You might want to check the connector or the actual wires themselves by testing the resistance from the O2 sensor to the DME. The wiring diagrams in the Bentley manual should help.

On a related note, I know for a fact that the smog stations don't plug in the car into their computer, so if there are any codes, the smog guys will not know about it. At least that's how it is for OBD-I.

-Wayne

Elfer · 09-07-2006, 06:59 AM

Thanks for the tips and reply Wayne. I don't know about OBD-1, but for OBD-2, the car obviously gets plugged into their computer. And if you had a code in the bank and erased it and immediately went to the SMOG station, the computer will fail your test due to no or insufficient data in the memory bank. Had this happen in my wife's ML. The tech took the test, the car passed the visual and numbers with flying colors. But because I replaced the MAF and then cleared the bank, the test failed on a technicality due to insufficient data. When was the last time you had your OBD-1 car tested? Not sure if they changed the way they test cars now. Anyone had their OBD-1 car tested lately and notice if the car gets plugged into the computer? Thanks.

Wayne 962 · Wayne 962's Garage

Your location says L.A., I'm guessing that's not Los Angeles, as they didn't do that with my BMW 5-Series (1998, ODB-II).

The ODB-I stuff is generally manufacturer-specific, so it would be difficult to test all the various types of cars...

-Wayne

Elfer · 09-07-2006, 10:51 PM

L.A. as in Los Angeles indeed. Glendale area to be precise. I even had the pleasure of having to go back to the SMOG station after driving the ML over 100 miles just to get some data log in the memory bank. I guess I'll have to find out for myself regarding OBD-1 testing. Ill take the car in tomorrow after erasing the memory and see if they hook the car up. If they do, then its check mate as there is no way the car will pass without any data. We shall see...

Wayne 962 · Wayne 962's Garage

Hmm, maybe I'm wrong - I can't remember them plugging in my E39 5-Series when it was time to be smogged...

-Wayne

wild97022 · 09-12-2006, 07:15 PM

MAYBE I AM OFF BASE, SO PLEASE FORGIVE ME. DOES ANYONE THINK THE CATALYTIC CONVERTER COULD HAVE ANYTHING TO DO WITH THE PROBLEM? MY 94 325 WAS SHOWING 02 SENSOR CODE, I REPLACED THE CAT, RESET AND PRESTO FIXED!

Elfer · 09-13-2006, 08:39 AM

Hmmmm......you may have a point. The cat is after the O2 sensor, but if its clogged, exhaust gasses might be accumulating in the exhaust system which would cause the O2 sensor to pick up readings that would be beyond acceptable range. Just a quick update, I haven't had a chance to get the car to a SMOG station. I will post results as soon as I do, which is probably this week. In the meantime, if anyone else would like to chime in and contribute any ideas or suggestions, please do so. Thanks.

Wayne 962 · Wayne 962's Garage

It's possible that the CAT may affect performance of the O2 sensor. On the later cars (ODB-II), the answer is a definite yes, as there are four O2 sensors (expensive to replace) on each side (before and after) of the CAT in order to measure that the CATs are working properly.

-Wayne

K2smitty · K2smitty's Garage

My 1995 325i would not pass omissions test in New Mexico! Had the shop replace my cats and finally it passed. Shop tech said that the cats were so clogged that he was surprised the car ran at all. My trip computer even showed a range increase of 75 more miles after replacing the cats. Now the car is throwing a 1221 code repeatedly after doing the stomp test. Trying to clear the code after replacing the O2sensor. Am I going to need to purchase a code reader to do this?

Farriri · 07-14-2014, 10:35 PM

Hi, got 318i e36 and ever since got 2years back just noticed my oxygen sensor at the exhaust isn't connect anywhere but has 2 wires hanging. want to find out if I can use the one from a 320i though it's a 93 model I should think and wanna put on a 94 318i

Farriri · 07-14-2014, 10:40 PM

forgot also on another related issue, the very 318i 94 has some sort of a pop sound at the exhaust while idling..or which was never there before, and sometimes the idle drops to like almost cut out and goes back to normal idle. no warnings lites really pop up except for one which after I put another airflow sensor seems to have disappeared. .A red exhaust like diagram with some 3 sort of waves on it.