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BMW 3-Series and 4-Series Forum (F30 / F32) | F30POST > Technical Forums > N47 and N57 Turbodiesel Engine / Drivetrain / Exhaust Modifications > Cheap NoX Sensor Question
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      01-16-2018, 12:48 PM   #1
kdog_x
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Cheap NoX Sensor Question

It's been cold in the Chicago area lately, and my 328d has been acting up. First it threw a code about the EGR drift being too high. So I removed the EGR, the internal valve was pretty cruddy, it wouldn't move smoothly when it was in it's fully open position. Cleaned it up with some carb cleaner and scrubbed the carbon off... no more issues. Reset all the engine lights.

About a week later the engine light comes back on, this time it says the front and rear NoX sensor is out of range. Reset the lights again.

3 weeks later it finally came back telling me the rear NOX sensor is out of range and SCR efficiency is off

So I performed the NoX sensor test with ISTA-D running and both sensors are functional and outputting readings. This time I reset the adaptations on the Nox sensors as well as resetting the lights, that was yesterday so we'll see how that goes.

Doesn't seem to be affecting the driveability at all, but I'm wondering if I may end up having to replace at least one of the sensors at some point if this comes back (unless these errors are just being triggered by the cold temps). As most of you are aware, the stealership wants $500+ each for these sensors... I notice that when I look up the dealer part number for the NOX sensors I find an $80 sensor from China that comes with the new sensor but no control module. Has anyone tried splicing one of these in? I would have to imagine the control module is still good and just the sensor needs replacement. It would appear you could use this as a front or rear sensor. $160 for a pair of sensors sounds better than dropping a grand if I have to go that route.

The emissions module on these cars is so flaky, I have a hard time believing that both sensors and the SCR module could be bad. Maybe one sensor... but it sounds to me like BMW just has some glitchy software.
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      01-19-2018, 12:04 PM   #2
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It is not normal to see these errors, maybe there is another problem with the car, you should do diagnostics first.
On my previous bmw I bought chinese oil level/temp sensor, that was adverticed to be very good. After change, the car stopped monitoring oil and I was about to crash when my engine shut off in a junction, because the sensor was reading 150 celsius on oil 10 min after cold winter startup.
So, no, never buy such important part from China!
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      01-19-2018, 12:13 PM   #3
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Thats definitely not good lol! After I reset the codes the last time and I topped off the def fluid just to make sure it wasn't empty. A little spilled out because it was quite full. Now it's throwing codes for the metering line heater short to ground and voltage too high.

Not sure if some def fluid spilled in the connector or something and shorted it out, not sure where it is or if thats possible. haven't had time to look at it. It looks like if I did short it out, I will have to replace the entire metering line. It sure seems like they built the DEF system to just barely outlive the warranty, I am at 70,000 now.
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      01-20-2018, 10:21 PM   #4
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Checked the metering line today. The heater wires were pretty crispy, only 0.5 ohms between so must be shorted. Ista+ says it should be 4.5-5.5 ohms. I ordered up a new line, hopefully thats the only issue. All of the electrical connectors were clean, no crystals of adblue or anything so not sure if I caused it from what I can see. Saw a pump pressure code as well, just hoping the pump is still kickin!
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      04-05-2018, 12:17 PM   #5
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kdog_x, did you find a solution to the Nox sensor issue? Was your car throwing a P229F code? That's what mine is throwing and I brought it to BMW to for diagnostics. They said 1 of 2 Nox sensors is bad and needs replacing...for $1,200! Wow! I am shocked at the cost to replace 1 sensor. I haven't had to replace anything else on my 2014 328d. If you can provide any guidance, I'd greatly appreciate it. What are the implications of waiting to replace the sensor?

I'm not having them replace the sensor, I'd rather learn to do it myself.
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      04-06-2018, 08:53 PM   #6
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Quote:
Originally Posted by haagm58 View Post
kdog_x, did you find a solution to the Nox sensor issue? Was your car throwing a P229F code? That's what mine is throwing and I brought it to BMW to for diagnostics. They said 1 of 2 Nox sensors is bad and needs replacing...for $1,200! Wow! I am shocked at the cost to replace 1 sensor. I haven't had to replace anything else on my 2014 328d. If you can provide any guidance, I'd greatly appreciate it. What are the implications of waiting to replace the sensor?

I'm not having them replace the sensor, I'd rather learn to do it myself.
If you do replace the sensor it is a piece of cake. I removed mine during deletes. It's identical to an o2 sensor replacement. One connector and remove the sensor from the pipe. I would recommend an o2 sensor socket though to make your life easier.
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      04-07-2018, 08:49 AM   #7
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Quote:
Originally Posted by rbreding View Post
Quote:
Originally Posted by haagm58 View Post
kdog_x, did you find a solution to the Nox sensor issue? Was your car throwing a P229F code? That's what mine is throwing and I brought it to BMW to for diagnostics. They said 1 of 2 Nox sensors is bad and needs replacing...for $1,200! Wow! I am shocked at the cost to replace 1 sensor. I haven't had to replace anything else on my 2014 328d. If you can provide any guidance, I'd greatly appreciate it. What are the implications of waiting to replace the sensor?

I'm not having them replace the sensor, I'd rather learn to do it myself.
If you do replace the sensor it is a piece of cake. I removed mine during deletes. It's identical to an o2 sensor replacement. One connector and remove the sensor from the pipe. I would recommend an o2 sensor socket though to make your life easier.
Thank you for sharing your experience and for the advice!
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      04-09-2018, 08:39 AM   #8
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Quote:
Originally Posted by rbreding View Post
If you do replace the sensor it is a piece of cake. I removed mine during deletes. It's identical to an o2 sensor replacement. One connector and remove the sensor from the pipe. I would recommend an o2 sensor socket though to make your life easier.
Interested to hear about your delete!? What tune are you running? What kind of power? How has it been reliability wise, have you put many miles on since delete?
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      04-24-2018, 03:19 PM   #9
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Quote:
Originally Posted by kdog_x View Post
Checked the metering line today. The heater wires were pretty crispy, only 0.5 ohms between so must be shorted. Ista+ says it should be 4.5-5.5 ohms. I ordered up a new line, hopefully thats the only issue. All of the electrical connectors were clean, no crystals of adblue or anything so not sure if I caused it from what I can see. Saw a pump pressure code as well, just hoping the pump is still kickin!
I think I might be confused but are you saying the line between your NOx sensor and the connector or where? Curious to see how this fix turned out!
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      06-07-2018, 09:48 PM   #10
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Guys, any Paul Harvey "Rest of the Story" on these cases?

My F31 328d started doing the intermittent engine light and I pulled the codes via Bimmerlink which indicated "DeNOx system efficiency: Efficiency too low in the range 1" (code 26F500) as well as "range 2" (code 26F600). I assume that one of those is the up stream sensor and one is the down stream sensor. If both are throwing a code would that mean that it is not the sensor itself but somewhere in the DDE (Diesel Digital Electronic) module???
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      06-07-2018, 10:14 PM   #11
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I stumbled upon the Technical Training Manual for the SCR2 and it seems that the DEF we have been putting in there may have changed the long term adaptations outside of the programmed tolerances. We have not been using the AdBlue brand lately but filling up from a DEF pump. Basically, the one we have been using may not have the same mixture as AdBlue and is not as efficient at converting the exhaust as AdBlue.

I don't know if I can drain the DEF tank, but I may try that and refill with AdBlue.
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      06-08-2018, 07:01 AM   #12
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Quote:
Originally Posted by M Pete View Post
Guys, any Paul Harvey "Rest of the Story" on these cases?

My F31 328d started doing the intermittent engine light and I pulled the codes via Bimmerlink which indicated "DeNOx system efficiency: Efficiency too low in the range 1" (code 26F500) as well as "range 2" (code 26F600). I assume that one of those is the up stream sensor and one is the down stream sensor. If both are throwing a code would that mean that it is not the sensor itself but somewhere in the DDE (Diesel Digital Electronic) module???
I wish. Next person that has a N0X issue needs to come back and tell us how they solved it! I feel like this will be an issue I see sometime down the line.
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      06-30-2018, 05:01 PM   #13
M Pete
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My hypothesis on mine is that it is all related to EGR valve malfunction brought on by a leaking EGR cooler. I think that it is letting more exhaust fumes down stream than what the car likes and the AdBlue can't neutralize it all. I should be replacing my EGR cooler and valve this next week so we'll see how my NOx codes respond.
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      07-10-2018, 10:10 PM   #14
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Quote:
Originally Posted by M Pete View Post
My hypothesis on mine is that it is all related to EGR valve malfunction brought on by a leaking EGR cooler. I think that it is letting more exhaust fumes down stream than what the car likes and the AdBlue can't neutralize it all. I should be replacing my EGR cooler and valve this next week so we'll see how my NOx codes respond.
Good thought. I wonder if that is the case on many of these failures? Any warning sign to the leaking EGR cooler?
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      07-10-2018, 10:36 PM   #15
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Quote:
Originally Posted by M Pete View Post
I stumbled upon the Technical Training Manual for the SCR2 and it seems that the DEF we have been putting in there may have changed the long term adaptations outside of the programmed tolerances. We have not been using the AdBlue brand lately but filling up from a DEF pump. Basically, the one we have been using may not have the same mixture as AdBlue and is not as efficient at converting the exhaust as AdBlue.

I don't know if I can drain the DEF tank, but I may try that and refill with AdBlue.

My 328d complained quickly about "incorrect fluid" when I used off brand stuff.
Oh, and gave me 200 mile countdown.

I refilled some with good fluid and reset the scr long term adaptation to reset mile counter. I have had to do that twice, diluting out the old stuff slowly. Didn't get to draining it yet.

But I started working on my SCR delete mods. We will see if I implement it. It's getting a bit annoying.
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      07-11-2018, 07:10 AM   #16
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Quote:
Originally Posted by Enabled View Post
My 328d complained quickly about "incorrect fluid" when I used off brand stuff.
Oh, and gave me 200 mile countdown.

I refilled some with good fluid and reset the scr long term adaptation to reset mile counter. I have had to do that twice, diluting out the old stuff slowly. Didn't get to draining it yet.

But I started working on my SCR delete mods. We will see if I implement it. It's getting a bit annoying.
I have heard some people that at least claim they used adblue but still get the incorrect fluid message. The consensus seems to be they end up replacing the NOx sensors. WOuld be nice to know if that is truly the root cause or not.
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      07-14-2018, 03:25 PM   #17
M Pete
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A week ago I replaced my EGR cooler and while I have no codes for EGR valve malfunction, I have gotten the NOx sensor code again. I have even ran down the DEF tank and filled it up with AdBlue. I will say that I used to get the NOX code daily after clearing it, but now only once in a week. I'll give it a little while to see if it adjusts. I know that a lot of things in BMWs have adaptations over time and shops usually reset those after they do work. I don't have that ability, so I'll just wait a little bit. It is not hurting the car any.
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      07-16-2018, 05:30 PM   #18
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Quote:
Originally Posted by M Pete View Post
A week ago I replaced my EGR cooler and while I have no codes for EGR valve malfunction, I have gotten the NOx sensor code again. I have even ran down the DEF tank and filled it up with AdBlue. I will say that I used to get the NOX code daily after clearing it, but now only once in a week. I'll give it a little while to see if it adjusts. I know that a lot of things in BMWs have adaptations over time and shops usually reset those after they do work. I don't have that ability, so I'll just wait a little bit. It is not hurting the car any.
What made you replace the cooler?
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      07-16-2018, 10:20 PM   #19
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There was a coolant leak inside it which also gummed up my EGR valve.
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      07-17-2018, 08:33 AM   #20
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Quote:
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There was a coolant leak inside it which also gummed up my EGR valve.
Interesting. What were the symptoms?
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      07-17-2018, 06:23 PM   #21
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I kept on loosing coolant but could not quite tell where is was coming from. Not any of the coolant pipes, the pump, or radiator. I could only see that some of the fluid had dried at the bottom of the splash guard below the engine on the passenger side. I also started getting fault codes saying that the EGR valve was too open and too closed, basically could not move. I took it to an indy shop to do a pressure test on it and the mech said that he could see it leaking in that area but could not tell exactly where without taking everything off the front, but suspected the cooler had a leak. The pressure test must have really opened up the hole because I started loosing coolant more rapidly during driving. When I pulled the cooler off I actually had to drain coolant from inside it. No issues since I changed it.
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