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Please help. Nox sensor issue on newly purchased 2012 35d

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56K views 97 replies 25 participants last post by  BimmerMan1975  
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#1 ·
On 1/19/16 I purchased a 2012 X5 35d. The car has 76K miles on it. I test drove the car for a bit and it drove well. I purchased the car out of state from a private seller, so once the seller and I completed the sales transaction, I drove around in my rental car to get a temporary plate.

I get back to the X5, install the temporary plate, and start heading back home to MI. Within 10 miles the service engine light comes on. I call the seller and he says he as no clue. I go to autozone and a NOX sensor and SCR (P2201 and P20EE) fault comes up. At this point all I can do is drive home b/c the deal is done. The seller tells me it has to be an error b/c he's never had an issue with the car before.

The next day I take it to a dealer in MI. They charge me $118 to run a diagnostic. The service manager tells me it could either be the NOX Sensors or the SCR catalytic converter. He then procedes to tell me, BMW requires the NOX sensors to be replaced before replacing the converter and that the NOX sensors are out of warranty but if that does not fix the issue, the converter is still in warranty and that would be replaced free of charge. He quotes me $1800 for the two sensors w/ installation.

I am confused on how BMW can force me to fix the NOX sensors and not be sure if that's the issue? What if its isn't? That means I'd pay $1,800 for parts that didn't need to be replaced. I told him to give me a cpl days to think about it. The dealership resets the code and I leave. So far, I have driven 100 plus miles and the engine light has not come back on.

How long would it take for the light to return if it truly is a NOX sensor issue. The seller owned the car for six months but only drove 1,000 miles (he said his wife did not like the heavy steering on the bmw b/c it made her arms hurt), so its been sitting a lot, could that have caused a false NOX fault? Should the engine light have come back on by now since I've driven 100+ miles? And can BMW make me fix the NOX sensors before they try to replace the converter?

I need to make a decision on whether to pay the $1800 for the sensors b/c I am at 77K miles now and the warranty on the converter expires at 80K miles. Thanks!
 
#2 ·
Next time get a PPI. You are not a car guy...failing to have it inspected will now cost you hundreds or thousands.

IMO the seller is a liar.

WHAT SPECIFIC CODES DID THEY PULL??????????????????????????????????????????????

Coming here, trying to escape a screwing by the dealer with only WORDS is not a very good tactical plan.

Have you read your warranty? Around the catalytic converter and 'what you need to do if you have a warranty claim'?


Back to the nox...you could probably create a document trail that, with legal threats, result in BMW paying for the NOX sensors if they do not fix the code. Force them to put in writing the following concepts:

There is a bad cat code
BMWNA insists we TRY the nox sensors even though there is no current evidence they are bad.

Now, based on your post I would bet money you will call the dealer and ask about my plan...and the dealer will lie to you and say 'we wont accept that- we need to do the work'..seen this play before.

Why not pay an indy half to replace the NOX sensors? Save the receipt. Still get the code, go back to the dealer and tell them it isnt the nox and pursuant to they printed warranty they need to fix the bad cat.
 
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#3 ·
ard said:
Next time get a PPI. You are not a car guy...failing to have it inspected will now cost you hundreds or thousands.

IMO the seller is a liar.

WHAT SPECIFIC CODES DID THEY PULL??????????????????????????????????????????????

Coming here, trying to escape a screwing by the dealer with only WORDS is not a very good tactical plan.

Have you read your warranty? Around the catalytic converter and 'what you need to do if you have a warranty claim'?

Back to the nox...you could probably create a document trail that, with legal threats, result in BMW paying for the NOX sensors if they do not fix the code. Force them to put in writing the following concepts:

There is a bad cat code
BMWNA insists we TRY the nox sensors even though there is no current evidence they are bad.

Now, based on your post I would bet money you will call the dealer and ask about my plan...and the dealer will lie to you and say 'we wont accept that- we need to do the work'..seen this play before.

Why not pay an indy half to replace the NOX sensors? Save the receipt. Still get the code, go back to the dealer and tell them it isnt the nox and pursuant to they printed warranty they need to fix the bad cat.
Click to expand...
Looking at the documentation the dealer gave me, there are no specific fault codes listed. Instead it refers to plausibility faults. Autozone pulled P2201 (NOx Sensor Circuit Range/Performance Bank 1) and P20EE (SCR NOx Catalyst Efficiency Below Threshold Bank 1). I looked at my warranty booklet regarding Federal Emission Warranty claims and this is what I found regarding how to file a warranty claim:

"Warranty claims must be made as soon as
reasonably possible after a defect is discovered.
To make a claim, the vehicle must be brought to
any authorized BMW SAV center during normal
business hours.
The authorized BMW SAV center will, without
charge for parts or labor (including diagnosis),
either repair or replace the defective part, if any.
The decision whether to repair or replace said
parts is solely the prerogative of BMW NA and
must be expected to correct the failure of the
warranted part. Parts for which replacements are
made become the property of BMW NA. In all
cases, a reasonable time must be allowed for
warranty repairs to be completed after the vehicle
is received by the authorized BMW SAV center."​

I plan to call BMW NA and to see if they'll cover the NOX sensor or authorize the catalytic converter replacement prior to making me pay for the sensors. What are your thoughts?
 
#5 · (Edited)
OP, you are rushing things for no reason. The vehicle is drivable - just take time to search the code on forums, look at SCR system (realoem.com), read up on warranties.
And take ard's advice (an ol' timer who been proven to know what he's talking about in matters like this).

At the very least, it appears only "pre-cat" sensor is bad (hence "bank 1"). That sensor is $220. The "post-cat" is the expensive one (not sure, I have seen someone say $1,500, for whatever reason).
 
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#6 ·
serge1 said:
OP, you are rushing things for no reason. The vehicle is drivable - just take time to search the code on forums, look at SCR system (realoem.com), read up on warranties.
And take ard's advice (an ol' timer who been proven to know what he's talking about in matters like this).

At the very least, it appears only "pre-cat" sensor is bad (hence "bank 1"). That sensor is $220. The "post-cat" is the expensive one (not sure, I have seen someone say $1,500, for whatever reason).
Click to expand...
Thanks for the advice. I guess my rush is b/c I have 77,300 on the car now and the warranty for the catalytic converter expires at 80,000 miles. As of this morning the light is still off. I have driven about 150 - 175 miles since they reset the light. Hopefully it stays off.
 
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#8 · (Edited)
Isn't it 7yr/70K in California? Technically the federal emission warranty does not apply to Michigan b/c an annual emission test is not required here. My car is still tregistered in MD b/c I haven't transferred the registration here yet (I'm driving on a 30 day temp plate).

Therefore, I'd have to get the warranty work completed (if the NOx sensors isn't the issue) before my temp plate expires and I have to register the car in MI as registering the car here could allow BMW to reject the warranty claim if the catalytic converter needs to be replaced. I researched MD's warranty and it didn't show they defaulted to California emission warranty, so the 8yr/80,000 warranty applies to my car until I register it in MI.
 
L
#13 · (Edited)
Never read NOx recall (the N47 in the 328d, but never read of one for the M57). There was a recall on the O2 sensor: maybe you guys are confusing?

Since I've run through the Rheingold diagnostics myself, here's again how it work.
1) The system turns off the urea metering valve
2) The technician drives the car to burn off any urea/ammonia stored in the SCR and saturate it with NOx to the point that it cannot process it anymore.
3) The technician gets back to the shop and plugs back in the computer. The computer reads the pre-SCR and post-SCR NOx sensor reading (Rheingold reports the processed signal in terms of ppm of NOx). Now that the SCR is saturate and no more NOx is process the two sensor should have a similar reading. The system allows up to 25% difference in the reading before a plausibility fault is triggered
4) The system identify the faulty sensor as the one of the two that has the lowest reading (that's the only mode a sensor can fail since it generates a voltage that is proportional to the amount of NOx that is present in the exhaust)
5) The technician replaces the faulty sensor and then carries out a recalibration test
6) It could result, subsequent to the calibration that the gap is still greater than 25% and the other sensor is asked to be replaced; HOWEVER THE FIRST DIAGNOSES RARELY REQUIRES THE REPLACEMENT OF BOTH SENSORS.

The reason is that these NOx sensor "age": by "aging" it means that the voltage they generate decreases and it's interpreted as less NOx than is actually contained. Mind that there is a "map" that accounts for this "aging" but perhaps they "age" after than expected. I'm still unclear what is causing the "aging": do they get poisoned by sulfur that albeit limited is still present in the ULSD (for example, the Lean NOx trap - LNT - that both VW and my 2012 Cummins use has a certain desulfation cycle and the chemical reaction that occurs inside the sensor is similar to what the LNT does on a greater scale; I don't think there's any desulfation taking place inside the sensor)? Do they get dirty with soot? There's no moving parts inside the sensor so they just don't wear, something else causes them to "age". It also seems that the pre-SCR sensor "ages" faster than the post-SCR so I'm leaning towards poisoning (by the time gasses get to the post-SCR they have less sulfur since it has a chance to deposit inside the SCR). But the post SCR sensor is also exposed to a great deal of vapor from both the water in the urea and created by the reaction occurring in the SCR so it could simply get "steam cleaned" on a regular basis.

This is just theory based on reading I've done and knowledge I have so it may be completely wrong...

Now let's say, for example, that Step 3 is carried out and the pre-SCR sensor reads 200ppm of NOx and the post-SCR reads 300ppm. Step 4 identify the pre-SCR as faulty (the difference is >25% and the pre-SCR is lower). You carry out Step 5 and the front now reads 450ppm (it's a new sensor). You still have a >25% gap between the two readings, but only now you know that the post-SCR has also aged beyond the acceptable limit.

I'm not sure there's a way to simultaneously diagnose both sensors, UNLESS the tech has already carried out the whole sequence with a test sensor. I doubt that's the case, but if he did, then he would also know whether the actual SCR is bad (which I highly doubt, but again, it is susceptible to sulfur poison, but so is the DPF which is upstream and I would guess would suffer more).

It is true that the status SCR cannot be diagnosed unless the performance of the NOx sensor is verified (the readings of the two is within 25% when the system is turned off)

Sorry for not answering your question, but I hope this helps...
 
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#15 ·
Wow! Thank you so much for that write up. Very detailed and well explained. After reading your post I have a question. Lets say you make several short trips (maybe three or four trips less than 5 miles) in a row where the engine cycles on and off. This will cause exhaust to go by the PreCat sensor immediately where it reads the level of NOx. But what if the short trips aren't enough to warm the catalytic converter up to be efficient resulting in higher than allowed NOx to be detected by the PostCat sensor? Could several short drives cause the car to read this as an error?

So for example: You start the car and the PreCAt sensor reads 500ppm. The exhaust then goes through the converter. Lets say the system threshold says the NOx level should be down to 200ppm at the PostCat sensor but b/c of the short trip its only down to 350ppm b/c the catalytic converter hasn't had a chance to warm up since the trips are so short. After multiple short trips of this occurring the car sends a SEL.

I ask this b/c I made a three to four short trips (less than a mile) and it was very cold outside. I guess the scenario/question doesn't address the plausibility test results but I just find it weird that the SEL hasn't come back on yet after two cycles of 50 plus miles of driving (know on wood). What are you thoughts or am I way off and being hopeful? I'm new to BMW and diesels (I came from an accord coupe which I knew a lot about) so I am still trying to learn things. Thanks!
 
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#14 ·
Originally Posted by CrashTest Dummy View Post
Car back. What they said: Recall Nox Sensor failed. Replaced.

What the report states: Connect battery charger, perform vehicle test. 4d16 SCR efficiency fault stored. Per test plan check level of AdBlue, check and clean metering module, check AdBlue with refractometer, all ok. Drive car for 30 minutes and read test results. Nox sensor before cat converter defective. Replace front Nox sensor, perform SCR adjustment, clear fault and road test. Ok at this time. diagcode; d1170-d0000000-10-001

1 13-62-8-576-471 SENSOR FOR NOX: 136099

All warranty work.

THIS WAS FROM THE POST I MADE EARLIER REGARDING MY ISSUE.
 
#17 ·
^ Just a quick opinion: if 3-4 short trips in the cold caused X5 diesels to trip nox sensor codes, there would be hundreds of posts about it.

BMW might even recall the sensors and change the programming. ;)

So while folks like to assume "I did X and Y happened, so X must have caused Y" I dont think so. Id assume BMW uses some sort of 'threshold of operating temp/time before executing such an internal test
 
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#18 ·
Yeah I agree. Thanks! I guess not wanting to spend the $ is making me reach for any possible cause other than needing a replacement lol. I've definitely learned my lesson. I've purchased two used cars prior to this and they were perfect, so I guess I let my guard down on this one. Definitely won't happen again.
 
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#19 ·
I don't have a recall number, but do remember my carfax from the dealer said NOX recall completed, along with a recall on the EGR bracket. When I got the CEL and took it to the dealer (a different one) they told me that the NOX that was replaced during recall had failed and it was replaced again.

BMW stating there are no open recalls on your X5 would make me guess that the original recalls were completed. However, not sure if your NOX failure relates to the original replacement. In any event, keep pushing on your dealer and if you do not get answers that you can live with, see another dealer. If you still feel price pressure see an independent.
 
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#21 ·
Based on the carfax history, the car has had extensive service at only two dealerships. I called both and they said they never replaced a NOx sensor. They've replaced a MAF sensor and O2 sensor as part of a recall but never a NOx sensor. I will try to contact a different dealer to see if they know anything about a NOx sensor recall or TSB. Thanks!
 
L
#20 ·
I continue to feel that CrashTest Dummy is confusing things. The work order he quotes is consistent with the diagnostic process of a NOx plausibility check not a recall. It was covered by warranty, but that doesn't mean it's a recall...

From my experience it seems that the NOx plausibility check is done over a rather long period of time: these codes come and go over many thousand of miles. I highly doubt driving cycles have anything to do with it. Also the way that the DDE carries out the plausibility test is possibly different than what Rheingold does. The latter shuts down the SCR system to do it; I'm not sure the DDE does the same or test it in some different way.

Like I said elsewhere, my car has the 4D16 set in the DDE; it has a 1 count and I believe it requires a count of 2 (or possibly more) to trip a CEL. I've carried out the Rheingold process which points to a pre-SCR NOx sensor. However I've probably put more than 500 miles and still the count is set to 1 and no CEL. That's why I feel these plausibility checks (like many plausibility checks) are carried out over a very long period of time before they become definitive.
Like I discussed elsewhere, my strategy would be to remove the sensor and soak it in some acetone or lacquer thinner to see if that does anything: I would be able to compare the pre and post treatment NOx reading to see if it helps.

Doesn't your (Chineywhale) workorder includes the actual BMW codes (they are 4 digit and don't have a P). I can't see the whole work order...

Good luck!!!
 
#27 ·
So thats your only choice, huh?

Why do we bother.....
 
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#26 ·
You paid $118 for a diagnostic. I'd ask for an actual diagnostic that one or both of the NOx sensors is bad per lpcapital's excellent troubleshooting steps.

Charging you $118 then just saying, "yea, we pulled the codes and don't know what exactly it is, first step is to blindly throw parts at it, then if it's still there, we'll blindly throw another part on it."

That's flat out lazy mechanic work right there. Call them on it, and say you specifically want a test done to SHOW that the NOx sensors are bad, and you want the details of that put on your service order for the work.
 
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#31 ·
So in addition to my NOx sensor issue, I went to have a key fob reprogrammed to the car. The SA told me 45 minutes. Four hours later he comes to me and tells me that they messed up some computer module and my brake lights and indicator lights for the car won't work. To add insult to injury, the module is on backorder from Germany and he has no idea when the part will be available. BMW is going to cover the module and they gave me a 2016 3 series as a loaner, but now I'm curious as to how long it'll take to get this module and how could they have messed it up. Its crazy to me to see that BMW's techs have issues diagnosing/fixing their own cars! It was a simple key reprogram!!! The SA told me he'd give me an update on Friday. If there's still no ETA on the part, should I contact BMW NA immediately so start a record of this? Thanks!
 
L
#32 · (Edited)
Let me paste here the PM you sent me, for the record so others may find the information in the future

Hello,

[...]. I got the specific codes from the dealer:

46B4: NOx sensor before DeNOx cat, plausibility NOx
4B6A: Nitrogen oxide sensor before SCR catalytic converter, plausibility
4D16: SCR system, efficiency

These codes all appear to point to the Pre-Cat sensor but my SA is telling me that its impossible for them to determine which sensor is malfunctioning from these codes, which is why they recommend replacing both sensors. What are your thoughts? Should I replace both sensors? Or try to replace to PreCat sensor and see if that resolves the issues?
Click to expand...
Below you find the description from the 3 codes: the only thing I see in common with them is "pre-SCR NOx sensor"... You can bring them to your dealer and show him.

I would also suggest you look around for the price of the sensor and have you SA price match it: what you get quoted for parts is 20% over MSRP and you often find 20% off MSRP.

13628576471 Front NOx Sensor

MSRP Core Save Online Price
$571.74 $0.00 $114.35 $457.39
Click to expand...
Source: http://www.getbmwparts.com/parts/in...rts/index.cfm?searchText=13628576471&make=BMW&action=oePartSearch&siteid=214672

You may also consider bringing your care to a different dealer if you don't feel they are treating you fairly... You shouldn't settle for anything but a professional and honest SA and I think you feel otherwise of yours.
 

Attachments

#33 ·
I had the 46B4 and 4D16 codes on the 2010 X5 w/ 71k miles along with codes for swirl flap actuator. Dealer recommended replacing both NOx sensors and doing a CBU cleaning on the intake and manifold. BMW agreed to cover (in my estimate) about 2/3 of the total cost for both as goodwill (the X5 is out of warranty) as I had the sensors replaced 26,000 miles ago under warranty and I've had issues with the swirl flap actuator before when the X5 was still under warranty. My out-of-pocket cost is $900 for the total work, which I am OK with. With all the issues BMW is having with the emission components and CBU on the diesels, I had hoped for a better offer from BMW. I am not complaining though, I think it's great that they acknowledge the issues we are having with the emission components and CBU. Otherwise, the X5 diesel is an excellent vehicle in my opinion.

To the OP, I suggest you get a 2nd opinion from another (better?) BMW dealer and ask for goodwill repair. It never hurts to ask, the worst they can say is no. Now when you know what the problem is, you can always find a reputable indy shop and have them fix it for you for less $. Good luck!
 
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#34 ·
Thanks to everyone for the continued suggestions. I am going to ask for a goodwill repair now that I have the codes. If that doesn't work, I am going to replace the PreCAT NOx sensor first since all the codes point to it. I actually found one for $220 from Southbridge BMW. The part number for the one I purchased is 13628511666. They explained to that it is same exact sensor as 13628576471 which the dealer quoted me $699 for. It was the last one they had in stock, so I purchased it. If it's the wrong one or BMW agrees to cover some of the cost, I'll just return it or keep it for the future (if it's the right part).
 
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#35 ·
I think you got it!!! Just a couple of followup things, to go along what ard said.

You want the SA to put in writing when you drop the car off:
1) You request all the old parts to be returned to you
2) You request them to put in writing in the final work order that they have completed any recalibration required by BMW diagnostic sowftare to be carried out subsequent to the replacement of the NOx sensor
3) You request them to put in writing in the final work order the NOx ppm reading for the pre-SCR and post-SCR sensors as reported by the BMW diganostic software as part of the diagnostic and post-replacement procedure. You'd like to have the reading both before and after sensor replacement.

Don't overlook the part where the SA puts it in the writing in the initial work order they give you when drop off the car.

I wouldn't settle for anything else: your SA has been too sketchy and too vague to be granted any more "benefit of the doubt"...
 
#37 ·
Goof advice above. One quibble- if BMWNA will be goodwilling or warranting any parts, they will likely NOT be able to give those back- so that one issue I would be flexibkle on. Everything else I would hold the line.
 
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#38 ·
Update: I got the PreCat NOx sensor in and took the truck to another dealer 50 miles away. They installed the sensor and completed the recalibration. The tech said he drove about 30 miles and re-performed the diagnostic test with no light or error. I purchased a wifi OBD reader a cpl of days ago and it too indicated there were no pending codes. Prior to the replacement, the engine light was off but the wifi OBD reader indicated there were the two same pending codes that would have eventually retriggered the engine light. This leads me to believe the issue is actually fixed. So instead of $1800 this whole thing cost me $450. Thank you guys so much for the help. I will keep you posted on whether anything changes. Now its time for me to replace these lower control arms. I found the write up and it looks super easy. Wish me luck!
 
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#40 ·
I'm glad you got it figured out. I just went through the same issue on a 2009. You can see the details of my story here: http://www.bimmerfest.com/forums/showthread.php?p=9514462&posted=1#post9514462. I wasn't able to discover the process of testing for each sensor as you have, even though I wondered about it a lot, so I ended up buying both sensors, I didn't realize you could use that 666 part in place of the 471 either. Both of these are very good tips for anyone else in with this issue wanting to save some money. Nonetheless, I was still able to save over $800 by using my indy rather than the dealer.
 
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#42 · (Edited)
Thanks! I actually got the part number from your post. Someone recommended it. I definitely wasn't going to replace the post cat sensor once all the codes that came up pointed to the precat. I would have fought BMW to the end if they required me to replace the post cat. But I got the confidence to challenge the dealer from this forum's support especially from lcapital and ard's tough love lol. Hopefully I can learn more abt bmws so I can contribute to this forum!
 
R
#45 ·
Same Thing PO 2201

I as well got the dreaded SCR/Nox code and luckily it was covered under the 7/70000 Ca emissions warranty. I took it in to the dealer here in Sacramento after much trouble shooting to simply avoid the trip! They call me the next day saying its going to be 2100.00 bucks to fix both NOx sensors and the exhaust temp sensor. The service advisor was nice but had no clue what was covered and what's not covered. He says "I spoke with the shop foreman and he says you have no warranty"! This immediately raised a flag and my blood pressure as I knew it was covered. So I tell them....piss on it I'll come pick it up! Then he goes on to say well maybe I can see if we can do a good faith repair to see if you can get a discount. I was getting irritated and asked to have them open a case with BMWNA. That changed his attitude quickly! After another day I get another call saying sir...your sensors are covered under the 7-70000 but the temp sensor isn't. So after I pick up the car, I asked them if there was a correlation with the temp sensor and the NOx sensors going south at the same time and the Tech says...no, that's just instructions from BMW. So the temp sensor stayed. I'll see if I get a code, more than likely not but we will see. What I'd really like to know is why these super expensive sensors go bad in the first place! I'm not looking forward to the next time this happens as I'll surly be over the 70k mark! :thumbdwn:
 
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