02 sensor failures

I have a 2006 e90 325i. I had an 02sensor failure code and replaced the front sensor as was the code. The next week the SES light came on ran the code and sure enough the same sensor. Pulled and replaced with a new part. Another couple of weeks later guess what? Yup the SES light and the same front 02 code and now the other front 02 code. Please help!

What exactly is the code saying? I ask because failure means what? Failure of the heater, failure of the thermocouple see what I mean. You could have a O2 heater failure that has nothing to do with the sensor but the heater wire may be broken causing the code.
If it is the thermocouple failing then you have either an electrical issue which would be pinched or broken wiring or an issue with one of the exhaust outputs killing the sensor. I am discounting anything with installation because if you have the ability to read the codes I assume the install was done correctly.

If you can post the exact code failure that would help a lot...

The code does not tell you what to replace. The code tells you what test procedure to follow, which will tell you what to replace. The code tells you that the signal from the 02 sensor is out of specifications. This COULD be because the sensor is bad. It could also mean that something else is wrong which is causing the 02 sensor to read Oxygen levels higher or lower than expected. Chances are the 02 sensor is fine and reading the oxygen level that is actually present. I heard one estimate that about 75% of oxygen sensors that are replaced are fine. There are no shortcuts, do the test indicated by the code and fix what is actually broken.

Originally Posted by haskindm

The code does not tell you what to replace. The code tells you what test procedure to follow, which will tell you what to replace. The code tells you that the signal from the 02 sensor is out of specifications. This COULD be because the sensor is bad. It could also mean that something else is wrong which is causing the 02 sensor to read Oxygen levels higher or lower than expected. Chances are the 02 sensor is fine and reading the oxygen level that is actually present. I heard one estimate that about 75% of oxygen sensors that are replaced are fine. There are no shortcuts, do the test indicated by the code and fix what is actually broken.

+1

Absolutely correct on all points! I would only add that there could be a recurring fault with the sensors, but it is being caused by something beyond the sensors' control. For examples, leaded gas will kill O2 sensors, so will silicone based additives or gasket material used on the induction system, and an upstream exhaust leak will cause a sensor to peg lean.
Find the cause!

Originally Posted by DSXMachina

....leaded gas will kill O2 sensors, so will silicone based additives or gasket material used on the induction system, and an upstream exhaust leak will cause a sensor to peg lean.
Find the cause!

What do you do to find exhaust leaks?

Thanks all For your responses! ill get the codes and post them in a little while.

Ok. The original code P112D. Then 2C3E and 2C3A now. Thanks in advance for all your input.

Originally Posted by CALWATERBOY

What do you do to find exhaust leaks?

I use a stethoscope for a quick and dirty, and a smoke machine for the tougher jobs. The smoker is the same one used to find vacuum leaks.

Originally Posted by SAVy?

Ok. The original code P112D. Then 2C3E and 2C3A now. Thanks in advance for all your input.

I believe the N52 had three sensors in '06. Two upstream and one downstream. Your code refers to the upstream Bank two sensor. Are you certain that's the one you changed?

Are the replacements from BMW? Platinum is costly and there are 'white box' no names floating around that don't last very long.

Originally Posted by DSXMachina

I use a stethoscope for a quick and dirty, and a smoke machine for the tougher jobs. The smoker is the same one used to find vacuum leaks.



I believe the N52 had three sensors in '06. Two upstream and one downstream. Your code refers to the upstream Bank two sensor. Are you certain that's the one you changed?

Are the replacements from BMW? Platinum is costly and there are 'white box' no names floating around that don't last very long.

I was sure there were four sensor two pre cat 2 post cat. I have not looked post cat. I replaced sensor number bank2 snsor1 the front most sensor linked to cyl 123 i think. The replacement did not come from BMW but were the proper Bosch part number. But i will check and recheck.

Multiple failures of the same sensor suggests something wrong with your wiring to the O2 sensor, sealant killing the O2 sensor prematurely or DME that is not reading the sensor input correctly. Also you can get other O2 sensor codes as I mentioned that have nothing to do with the sensor but the code you provide is the sensor.
Have you thought about swapping the 4-6 bank O2 sensor in place of 1-3 bank?
It is known to be a good sensor and if it comes up failed then you know it can't be the sensor.
It is hard to imagine multiple failures of correct Bosch O2 sensors.

Originally Posted by SAVy?

I was sure there were four sensor two pre cat 2 post cat. I have not looked post cat. I replaced sensor number bank2 snsor1 the front most sensor linked to cyl 123 i think. The replacement did not come from BMW but were the proper Bosch part number. But i will check and recheck.

Errrmmmmm, isnt the upstream sensor for cyl 4-5-6 the B2S1 sensor? You may have been changing the B1S1 sensor.

Originally Posted by DSXMachina

Errrmmmmm, isnt the upstream sensor for cyl 4-5-6 the B2S1 sensor? You may have been changing the B1S1 sensor.

Wouldn't that just suck. Better check my codes again.

Originally Posted by dsxmachina

i believe the n52 had three sensors in '06.

4

Originally Posted by DSXMachina

I use a stethoscope for a quick and dirty, and a smoke machine for the tougher jobs. The smoker is the same one used to find vacuum leaks.

Ultrasonic?

Originally Posted by CALWATERBOY

Ultrasonic?

LOL, you know too much, but no, I don't use the ultrasonic 'scope for exhaust leaks. They work real well for some vacuum leaks, but very poorly when you have the engine running and air is blowing over the probe. Then there's too much background noise.
I use a plain old stethoscope just like a doctor's, but instead of the solid hunk of ice which they have on the end to listen for chest sounds, etc., I have a probe. It is able to reach down into difficult access areas to pinpoint the source of a noise. Sometimes it gets whacked by a fan blade and then I can't hear anything for a day and a half.
They're especially useful for isolating bearing noise. Is that grind the ac pulley, the idler bearing, the tensioner bearing or what? No problem with a stethoscope. We used to use a long handled screwdriver and put our ear on the handle with the tip on a suspected part. For that customers don't want to pay $98/hr. Grab the stethoscope and they think that's cheap.

'Bigugly fab' posted "4" in regard to the total number of O2 sensors. I thought there was only one downstream sensor (and 2 upstream).


Too many engines, too few synapses left. Thanks for the correction.

Ok. So Im dumb. I now have 2 new sensors. The codes came back on. 2C3E and 2C3A. So much for savin a couple bucks. Its off to the dealer.

Originally Posted by DSXMachina

LOL, you know too much, but no, I don't use the ultrasonic 'scope for exhaust leaks. They work real well for some vacuum leaks, but very poorly when you have the engine running and air is blowing over the probe. Then there's too much background noise.
I use a plain old stethoscope just like a doctor's, but instead of the solid hunk of ice which they have on the end to listen for chest sounds, etc., I have a probe. It is able to reach down into difficult access areas to pinpoint the source of a noise. Sometimes it gets whacked by a fan blade and then I can't hear anything for a day and a half.
They're especially useful for isolating bearing noise. Is that grind the ac pulley, the idler bearing, the tensioner bearing or what? No problem with a stethoscope. We used to use a long handled screwdriver and put our ear on the handle with the tip on a suspected part. For that customers don't want to pay $98/hr. Grab the stethoscope and they think that's cheap.

Solution: Body English.

Pursed lips, furrowed brow; elegant flourish and careful, careful positioning, then thoughtful concentration. Clearly professional execution, they won't even notice the plastic O'Reilly's $10 'scope like I use for steam traps....