# NOx sensor replacement - thoughts?



## neill (Oct 4, 2004)

Hi all, I have a 2013 X5d with 115,000 km on it. CEL has been on for a while, and the diagnosis recommends replacing the two NOx sensors. I have just also replaced the EGR valve after the engine malfunction - reduced power light came on last month.

The replacement OE parts consist of the sensor, wire and module all in one, and are very expensive as a result. (Canada does not have the extended coverage on these components either). Any opinions on:
1) Does the failure happen at the sensor, or the module end?
2) Any experience with replacing the sensors only, and splicing in to the existing module? Sensors only are available on eBay. Less money for sure, but penny-wise, pound-foolish, or viable?
https://www.ebay.ca/itm/2PCS-8-wire...ash=item33e37d628f:g:gNkAAOSwbxpall6K&vxp=mtr

Thanks in advance!


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## Doug Huffman (Apr 25, 2015)

The sensors are cutting edge technology, particularly when compared to the electronics of the module. Most likely your sensor detectors have failed.

I was highly trained and experienced in the art of soldering. I would not recommend ***8216;splicing***8217; critical circuits without careful consideration.


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## neill (Oct 4, 2004)

I'm inclined to agree with you (even if the cost is going to increase by approx five-fold). I am hoping that there is someone that can report on a positive outcome going this way.


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## BimmerMan1975 (Jan 17, 2018)

I cannot say if that would work. When you say the diagnosis recommends?...Are you using software to get codes or was it a dealer?

I myself had the bad def 200 mile countdown happen to my 2014 535D. I ended up replacing both front and rear sensors at 1100.00 and come to find out there was a software glitch that was found a long time ago that messes with the diesel fluid introduction after a long while. After I reset the adaptations the codes went away and I've been error free for a few hundred miles now.

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## 328DxVancouver (Aug 27, 2017)

I would not do that. I wouldn't be surprised if the soldering messed up the resistance of the wire just slightly enough to cause issues in readings etc. As mentioned above those things are pretty delicate now days.
When i removed them from my 328d the module had to be replaced along with them ..... i don't believe they are cheap.


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## ard (Jul 1, 2009)

I would not be at all surprised if the module actually is 'tuned' to the sensor to which it is connected during manufacture. Essentially the two are a matched pair- 

In other diesel applications, you can re calibrate modules when a sensor is changed... wonder when someone will crack that nut for BMW diesels. (Send your old unit in, we replace sensor and re-calibrate)


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## neill (Oct 4, 2004)

Good feedback all. Thanks! I am def not going to buy the sensor-only parts. Too many variables


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## neill (Oct 4, 2004)

BimmerMan1975 said:


> Are you using software to get codes or was it a dealer?
> 
> I myself had the bad def 200 mile countdown happen to my 2014 535D. I ended up replacing both front and rear sensors at 1100.00 and come to find out there was a software glitch that was found a long time ago that messes with the diesel fluid introduction after a long while. After I reset the adaptations the codes went away and I've been error free for a few hundred miles now.
> 
> Sent from my SM-N950U1 using Bimmerfest mobile app


Codes read at the dealer level - I don't have them with me at the moment though.

I had not heard of a software issues - was it specific to F10 only?

Tks


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## imtjm (Oct 5, 2004)

i would first remove the sensors, see if there is build up, clean and then reinstall. if it works, then you are good to go. If not, you could do the resoldering. I don't prescribe that you couldn't resolder if you know how to properly solder. resistance is pretty easy to measure to ensure that you didn't muss anything up, but then again, if you know how to solder i'm not seeing the issue. with that said, I would be more inclined to buy the whole part anyway, since i see no advantage in replacing a new part of a part with an old part of the part when you are talking about a sensor.


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## Doug Huffman (Apr 25, 2015)

imtjm said:


> resistance is pretty easy to measure


Not when the measured resistance is comparable to the resistance of the meter leads, that is a mere conductivity measure. The resistance of a wire is measured with a 4-wire Kelvin Bridge.

ARD***8217;s suspicion of balanced sensor leads is appropriate as such a low voltage - hundreds of millivolts - measurement is likely by a bridge circuit.


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## BimmerMan1975 (Jan 17, 2018)

Took me a while to find it.















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## n00bkiller944 (May 21, 2018)

Did you end up replacing the sensor yourself?


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## BimmerMan1975 (Jan 17, 2018)

Yes.

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## n00bkiller944 (May 21, 2018)

BimmerMan1975 said:


> Yes.
> 
> Sent from my SM-N950U1 using Bimmerfest mobile app


Did you end up using an OEM part or aftermarket? How was the install?


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## BimmerMan1975 (Jan 17, 2018)

It was OEM. And the hardest part was removing the cover. The sensors are not hard unless they are frozen stuck. It was not a hard job. Depends on how handy you are though.

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## n00bkiller944 (May 21, 2018)

BimmerMan1975 said:


> It was OEM. And the hardest part was removing the cover. The sensors are not hard unless they are frozen stuck. It was not a hard job. Depends on how handy you are though.
> 
> Sent from my SM-N950U1 using Bimmerfest mobile app


Thank you for the information!


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## wufco1 (Jan 3, 2016)

There are multiple sensor along the exhaust; which sensors did you replace?


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