NOX diagnostic questions - upstream/downstream - P0097 DT (title change)

[Conor]

Please add a note to the beginning of the thread in bold "Please see post #4 on an update to this post and some new questions "

Hi Guys,

I am being quoted £358 (ex. VAT, Fitting) per NOX sensor and I need two, ahh!

I have learned there are fairly reputable aftermarket air suspension parts for the S212 at a significant discount. I am curious if the same can be said for a NOX sensor?

If so, how much should I expect to pay?

How specific are these to MB and the W/S 212 and M272 Petrol engine?

Thanks
Conor

 

[John Laidlaw]

I would steer clear of aftermarket NOX sensors, the Indies on here have written enough times of the problems these have caused. Not sure on price but give MB Grangemouth a call on 01324 686002 parts department, they are forum sponsors and give a lovely discount

 

[star]

You might need a star to code and update software and possibly change data card.

 

[Conor]

Ok, interesting. I guess as John has mentioned in a previous thread, calibrations et al need to be considered. Probably best to go OEM.

I have been investigating the reasons I think I need a NOX sensor.. an Indy has mentioned that I need to replace the two NOX sensor in the exhaust and would probably result in a failed emissions test at MOT. <-- this is an expensive repair!

I remember I took a picture of the error code on my scanner: 0097. B16(Right temperature sensor upstream of NOx storage catalytic converter). There is also an equivalent code for the left side too.

So, I have been googling this. While I believe the code is a generic OBDII one, it looks more like a sensor that is based up in the engine bay around the air intake. I have found a code P2000 which seems to be more in line with the sensor and explanation given by mechanic. (I may need to go back and scan the car with the engine running for a while and see if P2000 is in fact triggered).

There was also a mention of breathing and sampling air etc in an article I wrote. This has lead me to consider that either the sensors are bust or simply a bit messed up as a result of the oil leak in the engine, which has triggered the mechanic to quote replacing the "breather unit".

P.S. Is there an authoritative list of Mercedes Benz diagnostic trouble codes that I can refer to (with explanation) and take as gospel. I am uncomfortable with having to Google each code and be lead to a different page. - I would be willing to pay a small sum for access to this. Is it something that comes with "WIS"?

 

[Conor]

Ok, I spoke to MB Grangemouth -- very friendly guy in parts dept. (Thanks John!).

He has quoted me ~£95 inc. VAT each for left/right. And he has mentioned that these go "near the exhaust of the engine". And they are specifically temperature sensors (like my P0097 code says).

This requires further investigation I think - considering the price of buying and fitting two NOX sensors.

 

[star]

That’s too cheap for nox sensors. Quoted wrong part.

 

[Conor]

That’s too cheap for nox sensors. Quoted wrong part.

Ah but I wasn't asking about NOX sensors, that price is for temperature sensors up around the engine intake airflow I think. I think the reason NOX is referenced is because they are used to measure the intake temperature which has an effect on the combustion and production of NOX.

Are there any books I can read on the basic workings of a petrol engines? I don't want to try and become a mechanic or replacement of one but just something to give me a general understanding.

Thanks

 

[star]

Thread title asks about nox sensors?

 

[Blobcat]

Thread title asks about nox sensors?

Just changed the title at the request of the OP

 

[John Laidlaw]

Ok, interesting. I guess as John has mentioned in a previous thread, calibrations et al need to be considered. Probably best to go OEM.

I have been investigating the reasons I think I need a NOX sensor.. an Indy has mentioned that I need to replace the two NOX sensor in the exhaust and would probably result in a failed emissions test at MOT. <-- this is an expensive repair!

I remember I took a picture of the error code on my scanner: 0097. B16(Right temperature sensor upstream of NOx storage catalytic converter). There is also an equivalent code for the left side too.

So, I have been googling this. While I believe the code is a generic OBDII one, it looks more like a sensor that is based up in the engine bay around the air intake. I have found a code P2000 which seems to be more in line with the sensor and explanation given by mechanic. (I may need to go back and scan the car with the engine running for a while and see if P2000 is in fact triggered).

There was also a mention of breathing and sampling air etc in an article I wrote. This has lead me to consider that either the sensors are bust or simply a bit messed up as a result of the oil leak in the engine, which has triggered the mechanic to quote replacing the "breather unit".

P.S. Is there an authoritative list of Mercedes Benz diagnostic trouble codes that I can refer to (with explanation) and take as gospel. I am uncomfortable with having to Google each code and be lead to a different page. - I would be willing to pay a small sum for access to this. Is it something that comes with "WIS"?

Not sure how up to date this is, but it’s what I’ve used previously......

 

[Conor]

Thread title asks about nox sensors?

Yea, it started off as that kind of thread but turned into more of an investigation so I thought i'd change the title as opposed to creating another thread.

Not sure how up to date this is, but it’s what I’ve used previously......

Super, thanks, i'll give that a whiz, Cheers.

Just changed the title at the request of the OP

Thank you

 

[Conor]

I am very confused about going on here and I would really like to get a handle on whats going on. I figure I am second guessing this because of the codes appearing on my scanner and it just doesn't appear to pointing towards NOX sensor fault, given the error codes. That said, there is some behaviour of one of the NOX sensors I would like to query with you guys.

Just to recap

It has been recommended to me by an indy that I replace the two NOX sensors in the exhaust, indy said it's because "the NOX sensors are showing error codes".

I have scanned my car and receive the following codes on my scanner:
* 0097 - B16(Right temperature sensor upstream of NOx storage catalytic converter)
* 0101 - B16 /1(Left temperature sensor upstream of NOx storage catalytic converter)
- These codes are generic OBDII and according to the linked articles, they are relating to intake temperature and mass airflow.

After looking up NOX related codes, I have found MB specific codes (Thanks John):
* P2000 - NOx Trap Efficiency Below Threshold (Bank 1)
* P2001 - NOx Trap Efficiency Below Threshold (Bank 2) (Note this article, mentions upstream stuff and oxygen / MAF sensors). (It also talks about general connections and stuff.. my engine has an oil leak and supposedly there is oil all over the place. It has been mentioned that the breather box is covered in oil. I need to locate these sensors, and if there in that general area then we could be onto something as they could be generally mucked up by the oil). (This article also mentions operating voltages which I have not consciously checked, and may need to do so).

Now maybe I am wrong here (highly likely) but given the evidence, I would be think that a place to start might be in the upstream area as it is cheaper. Could start by replacing the breather box and discovering if the sensors are nearby, if so, then clean them with contact cleaner (or suitable). If persists, replace the sensors upstream.

If continues to persist, then check move down stream, but only after running an emission test in the MOT to be sure (Since there are no direct DTC appearing).

Now....
..keeping all of the above in mind, I want to show this quick video of me running a scan on the car while the engine is running. Please pay attention to values of (1)NOX Content Left/Right and (2)Power supply of component 'N37/5 Left/Right NOX control module.

I observed...:
(1) Left seems to be acting a bit weird and out of sync with the right reading -- not sure of the significance of this. Perhaps they normalise under normal driving conditions. i.e. Prolonged engine combustion at higher revs??
(2) The power supply readings of left/right seem to be a bit erratic. According to the P2001 above, the voltages should sit at about 0.5v

I'm not sure if the above observations are indicative of NOX downstream failure. Also, if it is, then it's strange that the codes aren't firing.

Are there any other tests I can run with the scanner?

What do you guys think, I hope you don't mind my being OTT on this but there is a huge difference in cost of the repairs, not to mention changing the wrong item will have the problem persist.

As one of the articles points out, freeze frame data is required to more accurately diagnose these issues. I understand what they mean but not sure I would be able to interpret the matrix of values and if my scanner can do it (I think it might be able to..).

References:
* Explanation of catalytic converter / emissions monitoring. Explains upstream and downstream, here.

Well, that turned out to be a long 'un. See you after tea