35D Active DEF tank forensics
 

So I finally got my hands on this broken active DEF tank for 2012 X535D. It is not a big deal to be opened, same as a gas tank screw-in cap on the top. It has 2 connectors with 8 wires altogether. 2 of them appear to be for a heater, 2 are for the temp sensor and 2 are for the level sensor and the other 2 probably for the urea quality sensor(someone please check the wiring diagrams). On the big connector 2 thick wires appear to be for the heater (you can see it on the bottom of the pot which goes inside the tank) and the other 2 are the temp sensor. The other 2 sensors are on the small connector.
I didnt have my thermometer with me, so I did a very rough measurments of the temp sensor resistance. So at around 65F it was 11k and went down to 7k when it was exposed on the sun for some time, roughly 85F.
I am sure a very simple emulator for the level and temp sensors could be made.
On to the pictures:

http://i1362.photobucket.com/albums/...psd2rhq9gf.jpg

http://i1362.photobucket.com/albums/...ps9ys2ef3y.jpg

http://i1362.photobucket.com/albums/...psh55wc2uw.jpg

http://i1362.photobucket.com/albums/...psatbdiadh.jpg

I like where you are going with this.

Yes!! Im hoping it wont be long till you come up with a solution for this issue :)
Keep up the great work!

Does this unit have a good temp sensor? If so, it looks like a 10k NTC thermistor will work. I have one I can send to anyone that wants to test it.

Keep in mind, this is a 4" long probe a wouldn't be a direct replacement, but could work as an emulator.

Various resistance values of this sensor:
24k ohms @ 45F
14.75k @ 60F
11.72K @ 70F
8.4k @ 85F

^^^ Looks like this will work.

I'm just curious about all of this, I do not have a Diesel, however, I like to understand the whys and why not of things.

1. I assume this "cup" goes into a larger tank? This assembly is somewhat like a fuel pump/sender that drops in a fuel tank?

2. Is there not a pump as part of this assembly? How does the Urea get out of the tank?

3. Is this assembly available separately or do you have to purchase and replace the entire tank assembly? Seems to me this could be/should be a serviceable part.

4. I assume the heater is the vertically mounted cylinder? Not sure this is a wise set up because I assume at times this "well" may not always be full? Maybe a heater coil in the very bottom would have been a better idea.

5. What is causing the temperature sensors to fail? I assume possible corrosion/liquid intrusion? Temperature sensors are typically pretty robust unless the problem is not with the sensor and it is with the wiring/connectors.

6. The top appears to be broken, was this from accident damage or trying to open and remove the insert?

Anyway, it will be interesting to see what can be done to improved on this. If BMW does not come out with a serviceable part, especially if the insert can be removed much easier than the entire tank assembly, I could see a possible market with what appears to be a higher than expected level of failures.

1. Correct.
2. No pump. I guess the fluid is scavenged and sucked from the tank by the exhaust.
3. The whole tank. The tank itself is probably the cheapest part, there is no reason for BMW to sell you what you see on the picture for 95% of the price of the whole assembly and risk a botched installation by inexperienced or careless mechanics.
4. Read my post. The heater is on the bottom of the cylinder.
5. Good question.
6. it was broken by car accident.
The overall design is not bad at all and it works fine when it works.

Thanks for the response.

I guess what gets me is if the heater/temp sensor module/canister could be easily replaced, even if I had to buy the tank, I might be inclined to just swap the heater/temp sensor module/canister.

But I am not seeing $800 or what ever in all of this.

We all know that restive heaters and thermistors are very low in cost.

Maybe the rotational/flow molding of the strange side tank is expensive?

There's no "urea quality sensor" -> the quality of the urea is assessed by changing the duty cycle of the metering unit and observing the shift in the post-SCR NOx sensor.
The 4 wires are all for the level sensor: there's a common, and 3 wires for the "FULL", "HALF" and "LOW" probes.

There is a pump, actually 2: there's a transfer pump and a supply module. The first one simply moves fluid from the passive to the active, the second one pressurizes the line going to the "metering unit" which is nothing more than in injector with some cooling fins.

Great work on this!!!!!

Which (I think) is why a 'bad urea' warning can be due to a clogged DEF nozzle: the duty cycle goes to its maximum limit; the DDE does not see the NOX values respond as they should; it then declares 'must not be def in the tank'

You get the idea, but there's an additional complication that doesn't allow a diagnosis by "maximum duty cycle"

The NOx sensor is not capable of distinguishing NO and NO2 (the NOx) from NH3 (ammonia, which is what the urea converts into once it hits the hot exhaust gas).

There is a phenomenon called "ammonia slip" that can occur when too much urea is injected. If there isn't enough NOx in the gas stream than some of the ammonia has nothing to react with and is emitted through the tailpipe which is something you don't want.

So the DDE changes the duty cycle to minimize the reading it gets from the NOx. A "high" reading could mean both too little urea (some NOx passes the SCR) as well as too much urea (some NH3 has slipped) and iteratively tries to target the low point. This is registered in an adaptation value to compensate for various tolerances in the system. The quality of the fluid is diagnosed by observing how marginal changes in the duty cycle affect the marginal changes in the NOx sensor reading, but also as sudden (meaning above a certain threshold) changes between the closed loop readings (the action-reaction of duty cycle to NOx sensor readings) and the adaptation tables.

Thanks for clarifying these tricky points. I just didnt have time to go thru the technology explanations.
There is also a control unit attached to the active tank, do you the purpose?

That is basically the pump that pressurizes (and evacuate) the line going to the injector in the exhaust.
It has another heating element in it (there's one inside the tank and one in the delivery unit).

It also evacuate the line before shutdown: this avoids DEF to christalize or freeze in the line going to the injector.

I am willing to be a test guinea pig on this if anybody wants to point me in the right direction. I can get any type of resistor if i know exactly what to buy, and if anybody can give me a some what of step by step direction, I have full access to the tank with the bad sensor and front bumper off the car for the next 2 weeks, i'm more than happy to experiment

One question, does the pump on top of the tank cycle 100% of the time or only at certain intervals? My pump does not show any codes whatsoever but also doesn't appear to be moving any fluid at idle ( I cannot test on the highway as the car is currently disassembled and this part is cracked

The pump only transfers DEF from the passive tank to the active tank when the level goes below certain treshold. My pump is bad and i have code for it, but it doesnt trigger CEL.

Oh, well this one is cracked from the accident I came across one earlier on eBay for $170 so I grabbed it vs $400 from BMW, I just want to avoid future problems

I have a 2 wire ntc thermistor in hand 50k ohm at room temp and goes down with heat applied, as well as a simple 2w 10k resistor

I just need to know what wires to splice now

^^^White and black wires on the big connector(smaller size). Thicker white and red are for the heater.
If it doesnt go much below freezing in your neck of the woods i would go with the resistor.

So just cut a splice both white and black wires and install the resistor between both wires vs in line with just one wire?

it hardly freezes here very often but if you have an ohm meter to read the resistance of the sensor in your damaged tank maybe using different temp ice water we could try to find a thermistor that would work properly in the system, if not no big deal.

I will try the 10k ohm resistor first and report back.


One other thing, this code is new. I am not sure what this code is. Driver detection?
http://s2.postimg.org/qb9ky5kbp/image.jpg

I think we have determined that the sensor is indeed a 10k ohm ntc thermistor. I don't think the 50k ohm sensor will work.

The resistor will go across both wires.

Ok, well I'll try the resistor first thank you

5pcs NTC 10K Ohm 1 3435 Thermistor Temperature Sensor Cylinder Probe 1 5M Wire | eBay

Would this work?

If it's rated 10k ohms @ 25c that should work.

IMO that may be a spurious error code due to a low voltage or glitch with a microcontroller on a CAN bus- possible a usb controller?

Would not be concerned- clear and see if it comes back when the car is buttoned, regularly driven with a good battery/charge

^^^^+1

Did you have a chance to try the resistor. I have the temp plausibility fault on my 2011 X5 35d and would like to avoid replacing the complete active tank.

Yes I tried a resistor and a thermistor and neither of them worked... I still have a check engine light and I still need help fixing it as well

any updates? Ive read about Jarek DPF delte, and i'm very interested in doing this. but not sure if it will fix my problem

Same issue?

http://www.xoutpost.com/bmw-sav-foru...-diesel-6.html

done any more since the last update 6 weeks ago?

i fixed this issue yesterday on an inventory vehicle at work
 

I found multiple fixes for this yesterday. I am a Nissan Master technician and work for a dealership. Yesterday we had an X5 with a check engine light on for the temp sensor malfunction inside of the active tank. I data monitored this issue and found sensor showing 25 degrees constant and it was currently 89 degrees outside. I gathered enough information from this thread to go into the tank myself and find a solution. I cut the wires going to the temp sensor and wired in a 10k 1/2 watt resistor and now my temp sensor shows 77 degrees all the time and killed the check engine light. I drove the vehicle home last night and back to work this morning and still no light. now I realize this fix wont hold up for when cold weather comes along, so I dug deeper to find a permanent fix. I found 2 options that work. I found that a standard fuel tank temp sensor from any of our Nissan vehicles will send the correct resistance value and is safe to drop inside of the active tank to correctly relay the right temp. option number 2 is slightly more costly, but it will fix this problem with a FACTORY style fix. I was unable to find a cheap BMW tank insert, so I got manufacturer names and sought the same part for other brand vehicles and hit gold on VW. here is a link to ebay for the part that matches the bmw part 100%

2007 2010 VW Volkswagen Touareg Heater Element for Urea Tank 7L6198970A | eBay

I hope this helps and I did photograph my adventure of fixing the tank with the 10k resistor.

Does anybody have a wiring diagram? I have a wire that has become separated in the harness, my temp sensor read fine inside the tank but I have a short to positive code

All the fuses In the box under the air cleaner are fine

go to google search and type in "bmw x5 active tank temp sensor wiring" the second picture is what I went off of. I have shopkey at work but the electrical diagrams for bmw are crap on there. that picture takes you to a thread on another forum where another guy used the 10k resistor and it worked for him also

Thanks for this, its a great contribution to this thread and im sure it will help someone when they need this fix.
You should do a DIY on this using the VW part, it would be the GoTo fix for this issue :thumbup:

If my company decides to buy the VW insert, I will definitely photograph and post the whole procedure. in the meantime, for anyone wanting to use the VW part, the removal is simple. take the front half of the inner fender down that's held up with several 8mm screws and push clips. the tank is then visible and fully accessible. remove the tank by disconnecting all of the lines at the quick connects (4 lines) and unplug the bulk connectors on the side of the tank nearest the engine (4 plugs) The tank is then only held in by two 10mm bolts up top and two 13mm bolts on the side nearest the engine and one grommet fitting on the bottom. once the tank is out, take out the three 4mm allen head bolts on top of the tank that hold the pump down. the insert is held in by a plastic ring that simply twists off. now pry the insert out lightly with a flat blade screwdriver and lift it about 2-3 inches up as this is all you will be allowed due to the inside connections limiting the free play. IMPORTANT... do not pull on the inside "cup" you have to insert your hand into the tank and turn the inside cup about 1/8th of a turn counter clockwise to release the cup and then the whole insert comes out and is ready for replacement.

Jesus, that is cheaper than sending to xemodex.

http://quirk-images.com/ebay01/ebayr...6198970A_1.jpg

That would be an AWESOME find if this works.

It will work. I took my insert out and apart and matched everything up. Same plugs and wire colors and connectors. My insert even had the same QR code picture on top and same yellow paint dot on top. Manufacturers part number matches as well.

Now I am angry, why would BMW not offer this and instead make people pay for an entire tank when the part is available from the manufacturer?

I wondered the same myself but from my experience with Nissan and Infiniti, some parts are available with Nissan that aren't available with Infiniti and are the exact same part. I believe the more expensive auto line uses tactics like these to maintain the "elite" status of their lineup so that not just anybody will be able to afford to own a BMW.

Thanks for the contribution!


I had an infiniti Q45 for many years and found this commonly. It took quite a few years for the DIY community to crack the Infiniti nut, (figure out how parts interchanged, learn lessons from other Nissan parts, etc) as it was a new marque at that time....

BMW just doesnt care about parts costs after 50k

https://www.ecstuning.com/Search/7L6198970A/ES2845755/

ECS Tuning has it for $227.

great find on the cheaper price!

Thank you, I am aware of that photo, unfortunately I need to trace back to the ecu Pinout as my wire has a break in it someplace.

Trolled the VW forums and found it even cheaper

7L6-198-970-A | REP KIT | VW OEM Parts | Genuine Volkswagen
$212.91

Great job guys :thumbup:

Thanks a lot for sharing your find!!! You are the first person to find a cheapest and proper factory fix option and it's gonna be a big help to BMW DIY community.:thumbup::thumbup:

You guys are very welcome. I don't personally own one of these fantastic rides, but after struggling with fixing one and finding a bunch of good information on this forum, I felt obligated to get a membership and share what I found with everyone in hopes to help ease the pain of this seemingly simple problem. Thank you guys for pointing me in right direction.

I wonder if they know this and hence how they make the quick repair and profit :dunno:

Yeah, I think BMW (as well as others) are banking on elite status and people who have money just to leave car there and pick up, sign bill and that is it.
Thanx for this. It is good that we are figuring out E70 fixes since I think this car with diesel engine has potential for lot;s of miles.

I agree mine has 115k miles and looks like new

My brothers E61 with 3.0ltr diesel single turbo (525d) in Bosnia made 270k km's before battery connection short circuited and burned car.

hey guys anyone tried the vw part in a 2012 x5d?
i've got the heater sensor error "4D32"

I was about to but my heater error code disappeared lol :dunno:

Get it from ebay, i seen it as low as $210 shipped from a VW dealer. Search for OEM part number. Sounded like its a plug and play since its the same BOSCH part BMW uses. If you do, take pics and such for a DIY writeup :thumbup:

lol wish mine would dissapear as well. most likely i will go this route. If i do will do a write up.

Not sure if its related but i got the BMW DEF, just so i have an easier way of filling the tanks in the future and i added it to the active tank, it took some. Then i added rest to the passive tank and i believe 2 days after doing that the code was gone. It could be coincidence but thats my story lol. No code yet since then :dunno:

apparently someone has already done DIY with pictures. and they also referred back to this thread.

Fault: Reducing agent, active temperature sensor- Code: 004D32 - Bimmerfest - BMW Forums