Oxygen senor question about voltage reading (not fluctuating)

[alex 1993 525i auto]

Hi all,

I had my oxygen sensor replaced 6 months ago after codes 1221 and 1222 showed up. I tested the sensor with my digital multimeter (DMM) and I was reading 0.30V from pins 1-2 with the engine hot and running and the sensor connected. The thing is that the voltage was not fluctuating like it was supposed to do as in the Bentley manual. The sensor was 60K miles old so I wanted to replace it anyways. I bought a Bosch (part no. 11-78-1-468-620) from Pelican Parts.

That fixed the issue for 6 months and now the problem is back. Same codes are showing up. If I clear them they come back right away when I start the car. I am doubtful that the sensor was good only for 6 months so I checked with my DMM. It again shows a non-fluctuating, 0.22V which very slowly increase to 0.27V in 5 min or so. Voltage is present at the connector pin 3-4 when the engine is running (13.3V) which means the heater relay is fine. There is continuity in pins 3-4 on the sensor side, with about 5 mOhms of resistance.

What I understand is that if the O2 sensor readings are out of the map, the readings will go to a default by computer to a non-fluctuating voltage, and 1221-1222 codes will show up.

http://www.opel-scanner.com/files/DME_1.1_1.3.pdf

(I now I have a Motronic DME version 3.3.1 but I couldn’t find better info).

I checked for vacuum leaks as it is often the case for O2 sensor codes but I couldn’t find any, I have 24’’ of Hg vacuum when I check from the brake booster connector. Intake manifold gaskets and MAF are less than 1 year old.

So I’m heading towards buying a new O2 sensor... this time I’ll get a BMW instead of a Bosch OE...
Is my diagnosis process good or I should check something else?

Thanks!
Alex

[shogun]

I assume it is not the problem of the manufacturer, you have to find out why they fail. Bosch is a good product (although I like the Denso or NGK sensors more) and BMW also does not make them on their own, it is probably Bosch and just the BMW logo is added.
What was the color of the sensors? Here are some pics http://www.walkerproducts.com/oxygen-sensor-faq/
" pulled my oxygen sensor and it is an orange/black/white color. What does this mean?"
Lead poisioning
antifreeze contamination
rich fuel mixture
silicone poisioning
Visual inspection will show signs of lead poisoning, antifreeze poisoning, silicone poisoning, and excessive oil consumption. When performing a vehicle tune up, remove the oxygen sensor and check for these common oxygen sensor conditions.

http://www.aa1car.com/library/o2sensor.htm
http://www.lambdapower.co.uk/diagnos...stic_index.asp

[Rustam]

You should check for the mixture blance. If the mixture is lean, the voltage does not fluctuate, but holds at atound .3 or lower. If the mixture is rich, the volrage hokds steadily at about .7 or higher.

Please ask Shogun to share my saved website address(I dont have a record of it its been too long). There is a procedure for AFM but other than this the steps are same. You should look for whatever gives ability to adjust mixture in your car and refer to the mentioned procedure.

[Rustam]

Shogun, you have the web saved version of my site with AFM procedure that explains the reasons and theory, which are still same for MAF case. The problem is addressed there.

[Rustam]

Hi all,

I had my oxygen sensor replaced 6 months ago after codes 1221 and 1222 showed up. I tested the sensor with my digital multimeter (DMM) and I was reading 0.30V from pins 1-2 with the engine hot and running and the sensor connected. The thing is that the voltage was not fluctuating like it was supposed to do as in the Bentley manual. The sensor was 60K miles old so I wanted to replace it anyways. I bought a Bosch (part no. 11-78-1-468-620) from Pelican Parts.

That fixed the issue for 6 months and now the problem is back. Same codes are showing up. If I clear them they come back right away when I start the car. I am doubtful that the sensor was good only for 6 months so I checked with my DMM. It again shows a non-fluctuating, 0.22V which very slowly increase to 0.27V in 5 min or so. Voltage is present at the connector pin 3-4 when the engine is running (13.3V) which means the heater relay is fine. There is continuity in pins 3-4 on the sensor side, with about 5 mOhms of resistance.

What I understand is that if the O2 sensor readings are out of the map, the readings will go to a default by computer to a non-fluctuating voltage, and 1221-1222 codes will show up.

http://www.opel-scanner.com/files/DME_1.1_1.3.pdf

(I now I have a Motronic DME version 3.3.1 but I couldn’t find better info).

I checked for vacuum leaks as it is often the case for O2 sensor codes but I couldn’t find any, I have 24’’ of Hg vacuum when I check from the brake booster connector. Intake manifold gaskets and MAF are less than 1 year old.

So I’m heading towards buying a new O2 sensor... this time I’ll get a BMW instead of a Bosch OE...
Is my diagnosis process good or I should check something else?

Thanks!
Alex

Here is the saved copy of my site from webarchive. Goto AFM Adjustment at left side:
http://web.archive.org/web/200704030.../e34a/id4.html

[shogun]

Yes, I saved it for you here http://twrite.org/shogunnew/otherMod...djustment.html

[alex 1993 525i auto]

Thanks for the link to the AFM adjustment but I mine is not adjustable I think, when I opened it last year it was just a small electronic card inside, no springs to adjust (part no. 13621747155).

As to the O2 sensor, I will try the trick to squeeze the fuel return line to make it run rich (or lean?) and to see if voltage jumps towards 0.8V (more V = more O2 reacting with the sensor?)... But the readings on the DMM were very steady close to 0.25-0.30V, they were not jumping at all between 0.2-0.8V like it should. https://www.youtube.com/watch?v=SLgdaWCuKVo
(close to when you test the AFM too)

Anyways like Shogun suggested I'd have the sensor removed , cleaned and tested out of the car if possible. Too bad I didn't keep my old one to compare...

[Last time I had the sensor replaced in a repair shop... I tried to do it myself but I can only put my car on ramps. There was not enough space under the car to remove the O2 sensor, I couldn't have enough torque on the sensor with the foot of space under there (it's between the cat. and the firewall). I guess I would need to lower the exhaust to get better access to the sensor? Even on the lift, the guys said it was not easy to remove...]

Thanks guys, let me know if you have other ideas/infos!
Alex

[shogun]

It might be that the wires are somewhere broken from sensor to Motronic. I usually check the O2 sensor on the motronic directly with engine running, engine must be at operating temperature. Do not know the pins on that Motronic, do you have to check on the online ETK the pins.
This is how it works http://www.bimmerboard.com/forums/posts/622383/
or the O2 sensor relay?
I also made myself a tester where we can easily see the bulbs fluctuating. exhaust, gas, oxygen monitor
Actually it is for this, bought it from Australia as a diy kit http://www.bimmerboard.com/forums/posts/606428/
http://imageshack.com/f/4noxysensortesterbs3p
Here we are testing it on an Alpina B12 E32, https://www.youtube.com/watch?v=K8miz_1aHYw

[Rustam]

Thanks for the link to the AFM adjustment but I mine is not adjustable I think, when I opened it last year it was just a small electronic card inside, no springs to adjust (part no. 13621747155).

?

I never implied nor stated that MAF would have a spring like AFM does. The idea that MAF has an electronic card inside is a well known fact. In fact I did say that MAF is different.

The implication was an adjustment screw, which some MAFs do have. The challenge was to look and see if yours is such, and follow the adjustment procedure.

[Rustam]

Yes, I saved it for you here http://twrite.org/shogunnew/otherMod...djustment.html

Thank you, Shogun, for your diligence.