# DEF Warning at 7000 miles



## dunderhi (Dec 10, 2006)

Not a real shocker given its happened to other 335d's. Rather than attempting to deal whether the dealer will top-off for free or not, I just went ahead and ordered 5 gallons for $21. I added on a couple of other items that doubled the weight of the order, and the shipping total was $21). So, I figure the DEF cost about $6-7/gal. Hopefully, the included spout will fit.


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## TDIwyse (Sep 17, 2010)

Along these lines . . .

I've read about adding DEF to the active tank and that part seems straight forward. Is there any reason you can't take the same approach and add to the passive tank? It has its own seperate filler port but I haven't read of anyone filling that tank. Anyone try it?

Where did you buy the DEF from? I've found several places locally that sell DEF but they didn't come with an adapter to the filler port. I've seen people buy the little DEF container from BMW which has the adapter for the port and have thought of going that route but I'd rather have something I could put on a bigger DEF container to minimizing the fussing around when doing a fill. 

Also, I'd like to hear about your bike rack and the bike you've got on it.


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## Snipe656 (Oct 22, 2009)

I know one person bought the BMW or maybe it was a VW bottle, used it and was planning to cut the end off to use with bottles they could buy cheaper elsewhere. Someone said the fill port is some sort of standard configuration used not just on BMWs. Would seem like an adapter must exist out there.


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## dunderhi (Dec 10, 2006)

TDIwyse said:


> Along these lines . . .
> 
> I've read about adding DEF to the active tank and that part seems straight forward. Is there any reason you can't take the same approach and add to the passive tank? It has its own seperate filler port but I haven't read of anyone filling that tank. Anyone try it?
> 
> ...


I don't know about filling the active tank, but I plan to add 2.5 gallons and see how far I get. Also, I just shopped around on the internet, and found some DEF at: http://www.discountfleetsupply.com/val729566.html From the picture, I see it comes with a filler nozzle, so I'm hoping it is compatible. I surfed the rest of the site and picked up some tire shine and interior cleaner.

The bike rack is the BMW rack that I ordered from Tischer. It works pretty well. I can install and remove the enitre set-up in a matter of a few minutes. I just need mrs dunderhi to help me carry to and from the roof of the car.


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## Dennis328i (Apr 5, 2007)

dunderhi said:


> Not a real shocker given its happened to other 335d's. Rather than attempting to deal whether the dealer will top-off for free or not, I just went ahead and ordered 5 gallons for $21. I added on a couple of other items that doubled the weight of the order, and the shipping total was $21). So, I figure the DEF cost about $6-7/gal. Hopefully, the included spout will fit.


I had the same issue a couple of weeks ago. "Exhaust Fluid Low" warning at 6300 miles. Took it to the dealer and gave my SA a copy of SI B 16 03 10. The tech determined the problem was "cause 2" per the SIB which is no transfer from the passive to the active tank. He trouble shot per SIB "procedure 2" and determined the transfer pump had lost its prime with fault code 46EB stored. He re-primed the pump and serviced the active tank with 2.5 gallons. No charge for the fix or DEF service.

They also did the software update on the ECU per SI B 13 03 10 while it was in.


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## Tedj101 (Nov 24, 2009)

Dennis328i said:


> I had the same issue a couple of weeks ago. "Exhaust Fluid Low" warning at 6300 miles. Took it to the dealer and gave my SA a copy of SI B 16 03 10. The tech determined the problem was "cause 2" per the SIB which is no transfer from the passive to the active tank. He trouble shot per SIB "procedure 2" and determined the transfer pump had lost its prime with fault code 46EB stored. He re-primed the pump and serviced the active tank with 2.5 gallons. No charge for the fix or DEF service.
> 
> They also did the software update on the ECU per SI B 13 03 10 while it was in.


Where did you get the SIB? I'd love to have a copy...


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## tlak77 (Aug 5, 2009)

Tedj101 said:


> Where did you get the SIB? I'd love to have a copy...


Search for it Ted in this section DEF subject has been bitten to dead; and all related SIBs are here.


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## need4speed (May 26, 2006)

dunderhi said:


> I don't know about filling the active tank, but I plan to add 2.5 gallons and see how far I get. Also, I just shopped around on the internet, and found some DEF at: http://www.discountfleetsupply.com/val729566.html From the picture, I see it comes with a filler nozzle, so I'm hoping it is compatible. I surfed the rest of the site and picked up some tire shine and interior cleaner.
> 
> The bike rack is the BMW rack that I ordered from Tischer. It works pretty well. I can install and remove the enitre set-up in a matter of a few minutes. I just need mrs dunderhi to help me carry to and from the roof of the car.


Let us know how this works out. How easy is it to use and does the D seem to run the same with this as what ever the factory put in. N4S


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## Snipe656 (Oct 22, 2009)

The fluid has been hashed out many times before, the consensus was there is nothing special about the fluid BMW puts in v. the stuff sold else where. People brought up all sorts of specs and such to prove their point at the time.


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## dunderhi (Dec 10, 2006)

need4speed said:


> Let us know how this works out. How easy is it to use and does the D seem to run the same with this as what ever the factory put in. N4S


UPS says it will get here on Tuesday, so I'll pass the results then. If it needs more than a top-off, I call the dealer on Wednesday.


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## dunderhi (Dec 10, 2006)

The DEF arrived today and here's what happened.

First, the nozzle supplied with the did not work. The nozzle fit in the port, but without a tight seal, it quickly overflowed. Luckily, I had covered the car with a plastic bag. Next step, I got a flashlight to see where I went wrong. The actual opening is about the size of a pen, so either I needed to find a nozzle adapter that was pen sized (paging Mr. McGyver?), or find a nozzle that would make a tight seal with the port. The later worked just fine with a funnel I had lying around. I needed to sand the funnel a small amount, but after that it provided a urea tight fit. It was a slow fill process, add a cup or two and wait 10-20 seconds for it to drain. I eventually added a gallon or so, and took the car for a test drive. Within a quarter mile the low DEF went out. Mission success for about $7. :thumbup:


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## F32Fleet (Jul 14, 2010)

dunderhi said:


> The DEF arrived today and here's what happened.
> 
> First, the nozzle supplied with the did not work. The nozzle fit in the port, but without a tight seal, it quickly overflowed. Luckily, I had covered the car with a plastic bag. Next step, I got a flashlight to see where I went wrong. The actual opening is about the size of a pen, so either I needed to find a nozzle adapter that was pen sized (paging Mr. McGyver?), or find a nozzle that would make a tight seal with the port. The later worked just fine with a funnel I had lying around. I needed to sand the funnel a small amount, but after that it provided a urea tight fit. It was a slow fill process, add a cup or two and wait 10-20 seconds for it to drain. I eventually added a gallon or so, and took the car for a test drive. Within a quarter mile the low DEF went out. Mission success for about $7. :thumbup:


The nozzles should be universal. Curious why did you not have the dealer address this?


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## dunderhi (Dec 10, 2006)

BMWTurboDzl said:


> The nozzles should be universal. Curious why did you not have the dealer address this?


No appointment to schedule.
No getting up early to drive to the dealer.
No loaner car.
No leaving work early to return the loaner.
No $40/gallon BMW DEF.
No frustration when the dealer did something wrong.


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## jtc424 (Oct 16, 2010)

so do we know for a fact def fluid is not covered in ultimate service?


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## TDIwyse (Sep 17, 2010)

Thanks for the update dunderhi. I anticipate having to do something like this at some point in my ownership period and am interested to learn from others experiences.


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## dunderhi (Dec 10, 2006)

jtc424 said:


> so do we know for a fact def fluid is not covered in ultimate service?


It is covered at the normal service intervals, but different dealers have different opinions about off-cycle fills. In my opinion is it's not worth the bother.


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## jtc424 (Oct 16, 2010)

dunderhi said:


> It is covered at the normal service intervals, but different dealers have different opinions about off-cycle fills. In my opinion is it's not worth the bother.


Gotcha, thanks for the heads up Dunderhi


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## mecodoug (Nov 30, 2007)

I noticed today that Bavarian Autosport (bavauto.com) has 2.5 gallon DEF as well.

I don't know if they are all the same but I expect they are - I think it is OEM at that site but it is a few more $.


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## Dennis328i (Apr 5, 2007)

dunderhi said:


> No appointment to schedule.
> No getting up early to drive to the dealer.
> No loaner car.
> No leaving work early to return the loaner.
> ...


Chances are you haven't fixed the source of your low fluid warning. If your transfer pump has lost its prime and is not moving fluid from the passive to the active tank, then as soon as the active tank gets low again your going to get the DEF warning.

If you make it to your scheduled oil change without getting another DEF warning, suggest you tell your SA what you just went through and have them check the system per SI B 13 03 10 to verify your transfer pump is working. BMW has acknowledged the issue, thus the SI B so its a no-charge fix.

Good luck !


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## dunderhi (Dec 10, 2006)

Dennis328i said:


> Chances are you haven't fixed the source of your low fluid warning. If your transfer pump has lost its prime and is not moving fluid from the passive to the active tank, then as soon as the active tank gets low again your going to get the DEF warning.
> 
> If you make it to your scheduled oil change without getting another DEF warning, suggest you tell your SA what you just went through and have them check the system per SI B 13 03 10 to verify your transfer pump is working. BMW has acknowledged the issue, thus the SI B so its a no-charge fix.
> 
> Good luck !


I'll let the dealer know what happened, but I guess my question is whether I added DEF the active tank or the passive tank - I'm not sure. Anyone know? Since I only added a gallon or so, no matter which tank I added to, I suspect I'll get the warning light again in about 2,000 miles.


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## Tedj101 (Nov 24, 2009)

?


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## mecodoug (Nov 30, 2007)

This shows which fill portal is which on an E90. #1 is the active port (on the bottom.)


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## dunderhi (Dec 10, 2006)

mecodoug said:


> This shows which fill portal is which on an E90. #1 is the active port (on the bottom.)


I filled the active port (#1). Do you think that might imply #2 is the passive port?


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## MrBonus (Jun 26, 2010)

Great, my warning light came on at 4900. I hope this doesn't become a regular nuisance.


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## TDIwyse (Sep 17, 2010)

dunderhi said:


> I filled the active port (#1). Do you think that might imply #2 is the passive port?


I think#2 is the passive tank port. I opened both ports up last night and they seem to have the same shape/design. I'm still curious if anyone has tried to fill the passive tank. After the 4 yrs maintenance coverage is done I can't see myself paying the dealership to do this . . .


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## jtc424 (Oct 16, 2010)

MrBonus said:


> Great, my warning light came on at 4900. I hope this doesn't become a regular nuisance.


me freakin too...


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## Snipe656 (Oct 22, 2009)

After four years this stuff is going to be very common placed giving how many old cars and trucks will use it. Someone on here said he did all his maintenance since day one but I don't recall him getting detailed about his def refills. Why would it not just be hooking the container to the other port?


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## jtc424 (Oct 16, 2010)

http://www.bmwtis.com/tsb/bulletins/bulletin_graphic_temp/b160310g.htm


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## Snipe656 (Oct 22, 2009)

Seems a lot of the people get low def warnings and it simply was because both tanks were not full at the beginning. It is a real shame they do not provide us with a way to gauge the amount of def in each tank.


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## bimmerdiesel (Jul 9, 2010)

TDIwyse said:


> I think#2 is the passive tank port. I opened both ports up last night and they seem to have the same shape/design. I'm still curious if anyone has tried to fill the passive tank. After the 4 yrs maintenance coverage is done I can't see myself paying the dealership to do this . . .


I am ready to spend an hour for every 2-3k miles instead of dealer visit. I havent got DEF warning till date so havent tried even opening the cap but if at all I get just like OP I would try it out myself and see how things go


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## mecodoug (Nov 30, 2007)

Yes #2 is the passive tank. I think you may not want to only fill the active tank as the def in the passive tank will get too old.


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## mecodoug (Nov 30, 2007)

bimmerdiesel said:


> I am ready to spend an hour for every 2-3k miles instead of dealer visit. I havent got DEF warning till date so havent tried even opening the cap but if at all I get just like OP I would try it out myself and see how things go


It should be an hour every 12-15K miles if you fill both tanks.


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## bimmerdiesel (Jul 9, 2010)

mecodoug said:


> It should be an hour every 12-15K miles if you fill both tanks.


thats even better.


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## Diesel Power (Oct 2, 2010)

*DEF Service Light*

The DEF service warning light just activated on my 2011 335d at 6,771 miles. I have a service appointment scheduled to replenish tomorrow. We'll see if any OBD fault codes are stored.


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## 62Lincoln (Sep 26, 2004)

If the opportunity presents itself, I would love to hear how they explain the need to replenish the DEF at this mileage.


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## F32Fleet (Jul 14, 2010)

Diesel Power said:


> The DEF service warning light just activated on my 2011 335d at 6,771 miles. I have a service appointment scheduled to replenish tomorrow. We'll see if any OBD fault codes are stored.


I think there's a chronic case of underfilling at the factory.


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## Snipe656 (Oct 22, 2009)

Wonder if enough people complained about wanting a way to gauge the level in the car if they'd add that, yeah I know that is just dreaming on my part.


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## tlak77 (Aug 5, 2009)

Snipe656 said:


> Wonder if enough people complained about wanting a way to gauge the level in the car if they'd add that, yeah I know that is just dreaming on my part.


I did, even send an email while back to BMW NA, also asked bavarian technic (since I have their cable) to add option of checking level sensor data for active and passive tank. I doubt anything will come out of it.


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## Neutrinolad (Jun 23, 2009)

Is that a Specialized road bike you got there? Nice to see some other riders here in the d forums.


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## dunderhi (Dec 10, 2006)

Neutrinolad said:


> Is that a Specialized road bike you got there? Nice to see some other riders here in the d forums.


It's a Velo Vie.


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## Diesel Power (Oct 2, 2010)

The dealer added 2.5 gallons of DEF and needed to drive the vehicle around for several minutes in order to reset. I was told they couldn't reset via the computer (not sure why). Headed out of town for the Thanksgiving holiday (1,600 miles round trip). My 335d performed flawlessly during the 10-hr extended drive. No more problems with the DEF warning.


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## MrBonus (Jun 26, 2010)

My car has a fault that isn't allowing transfer between the active and passive tanks. I've got a Pontiac Vibe on loaner. So much fun.


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## F32Fleet (Jul 14, 2010)

MrBonus said:


> My car has a fault that isn't allowing transfer between the active and passive tanks. I've got a Pontiac Vibe on loaner. So much fun.


I wish someone could chime in with regards to the reasoning behind having an active and passive tank. Seems needlessly expensive to build.


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## MrBonus (Jun 26, 2010)

BMWTurboDzl said:


> I wish someone could chime in with regards to the reasoning behind having an active and passive tank. Seems needlessly expensive to build.


No kidding. It seems like another item that's there to create service revenue.

I wonder if it's simply cost prohibitive to keep an entire 6 gallon tank heated so they have the smaller, heated primary with the unheated secondary tank.


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## Penguin (Aug 31, 2003)

MrBonus said:


> No kidding. It seems like another item that's there to create service revenue.
> 
> I wonder if it's simply cost prohibitive to keep an entire 6 gallon tank heated so they have the smaller, heated primary with the unheated secondary tank.


I suspect it has to do with the battery drain required to heat the entire supply of DEF, e.g., when it get's below 10-20 degrees F, you want to minimize the drain on the battery while the vehicle is sitting.


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## MrBonus (Jun 26, 2010)

Penguin said:


> I suspect it has to do with the battery drain required to heat the entire supply of DEF, e.g., when it get's below 10-20 degrees F, you want to minimize the drain on the battery while the vehicle is sitting.


That certainly makes sense.


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## MrBonus (Jun 26, 2010)

For anyone interested, they ended up replacing the transfer pump between the two tanks. This was the cause of my DEF warning coming on at only 5000 miles. I'm wondering if this is the cause of anyone else's woes as well. The dealer elected to pull codes when they went to refill due to the unusually low mileage of the required refill and that's how they isolated the problem.


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## 62Lincoln (Sep 26, 2004)

Thanks for sharing your outcome, the fix makes perfect sense. Hope this is the end of your DEF saga!


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## Snipe656 (Oct 22, 2009)

I just got the 999 warning today. Car has around 12.5k miles on it. I am not sure when my first oil change was done, I guess around 6-7k miles. I know it was completely drained and filled when that change was done. My car currently says 4600 until next oil change so would dare say the light is on a little soon. The car is due for the second oil change though because it has been 12 months. I will take it in next month since then it also will need a state inspection. Will see if it is just low on fluid or some sort of tank transfer issue.


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## magbarn (Jan 28, 2003)

UhOh! My turn. Car only has 6200 or so miles. I guess BMW isn't filling up the DEF tanks at the dealer!


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## Snipe656 (Oct 22, 2009)

Dealer told me today that BMW only pays them back for DEF when it is done with an oil change that also is being paid for by BMW. They did not seem to think it was an issue that my car used up so much DEF in this many miles. I am guessing they will put next to no effort into looking into it. So will wait and see if it happens again then become an asshole about it.


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## Penguin (Aug 31, 2003)

Snipe656 said:


> They did not seem to think it was an issue that my car used up so much DEF in this many miles.


I sometime get the feeling that if I drove my X5 into the dealer with flames coming out of front of the vehicle and a burning trail of diesel fuel behind it, they wouldn't think it was an issue, and would calmly offer to sell me a BMW branded fired extinguisher for $499.


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## Snipe656 (Oct 22, 2009)

Penguin said:


> I sometime get the feeling that if I drove my X5 into the dealer with flames coming out of front of the vehicle and a burning trail of diesel fuel behind it, they wouldn't think it was an issue, and would calmly offer to sell me a BMW branded fired extinguisher for $499.


Funny. The entire way that he responded to me came off like I am not the first person coming in with this stated issue. My DEF fillip will be for free though due to tha annual oil change so right now I am not worried about it but more curious as to why it happened.


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## Penguin (Aug 31, 2003)

Snipe656 said:


> I am not worried about it but more curious as to why it happened.


I would guess that the primary tank was not full when shipped from the factory.


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## Snipe656 (Oct 22, 2009)

I was present when the first oil change was done and I know both tanks were filled up then, it was one of the reasons I was stuck at the dealership for much longer than they originally anticipated. The factory charge of DEF never posted a warning before the first yearly oil change.


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## DnA Diesel (Jul 31, 2010)

The DEF fill warning is linked only to the fluid level in the active tank (1.6 gal). The BMW engineers assumed that the passive tank (4.5 gal) would empty fully before the level of the active tank would drop. Unfortunately, the system does not account for a failure to transfer DEF from the passive tank to the active tank. This failure to transfer could happen for a number of reasons, the most likely being: a) a failure of the transfer pump, and b) sustained sub-zero temperatures where the DEF in the heated active tank is consumed and the frozen DEF in the un-heated passive tank cannot flow into the active tank. The resolution to the first problem is getting the transfer pump repaired, and to resolve the second, the car needs to be brought into a warm enough area so the DEF in the passive tank thaws and can be transferred. Engineering-wise, I can see why BMW designed the warning system as they did; their assumptions are fair if all is working as designed, and to be fair, the owner's manual does comment on the possibility of the passive tank freezing for extended periods, so the folks in Munich were definitely aware of the possibility. That said, I am surprised that a failed DEF transfer pump would not trigger a BC/Check Control warning to the driver; it must be stored as a hidden code within the DME.

On its own, the 1.6 gal active tank should last for approximately 50 to 75 gal of fuel consumed (at 3 to 2% DEF consumption respectively). Pure highway driving at a representative 38 mpg would net a best case range until DEF refill of 2850 mi (2% DEF consumption rate). 'Led-footed' city driving at 26 mpg would result in an 'active tank only' range of 1300 mi (3% DEF consumption rate).

I myself have never had a 'frozen passive tank' induced DEF refill warning, and that's driving for some relatively long cold periods in places up in Northern Ontario, so I doubt that anyone else would experience that either (perhaps a Minnesotan 335d driver during a long cold-snap?), so I would deduce that the most likely cause for the DEF warning (assuming the vehicle was filled fully in Munich) is a transfer pump failure approximately 1000-2000 miles prior to the initial warning.

Aside, there's a body pan underneath and I can't see any access panel from inside the trunk to determine the level of fluid in the larger passive tank, so the above would be a theory that remains to be proven. 

Regards
D


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## Kanuck (Feb 18, 2003)

DEF warning came on in my car at about 8000 miles after it had been sitting unused for a few days at somewhat cold temperatures (-10C/+14F). Added 0.5 gallons of DEF to active tank using BMW supplied bottle ($22) that screws on. Very easy. Warning light went out in a few seconds of driving. When temperature rose to +10C/+50F I tried adding DEF to passive tank but it appeared to be full (not sure why, as it should not be full after 8000 miles).

I am assuming that DEF in passive tank froze, although I don't know how you can tell if it is actually a pump problem without taking it to a dealer. I guess once spring comes and if active tank keeps running dry, then it is a pump issue.

According to SI B16 03 10, DEF will freeze at temp below 25F. That is not very cold.

Does the passive tank get heated at all, even indirectly, when the engine is running? In other words, maybe the fact that my car sat for a few days in cold had something to do with it?


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## Snipe656 (Oct 22, 2009)

Kanuck said:


> According to SI B16 03 10, DEF will freeze at temp below 25F. That is not very cold.
> 
> Does the passive tank get heated at all, even indirectly, when the engine is running? In other words, maybe the fact that my car sat for a few days in cold had something to do with it?


That is very cold around here 

Maybe it is close enough to the exhaust to indirectly get heated by that?


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## DnA Diesel (Jul 31, 2010)

No, there isn't any heating in the passive tank. If you use up the active tank and the temperature remains below the DEF's freezing point, you will get the warning.

On another note, I understand from talking to a master technician at the dealer that only the active tank can be feed externally by bottle from the DEF fill ports. The passive tank requires the car being being hooked up and the transfer pump run in reverse to transfer from the active up into the passive tank, hence why a full flush and refill takes a while. 

Regards
D


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## Penguin (Aug 31, 2003)

DnA Diesel said:


> The passive tank requires the car being being hooked up and the transfer pump run in reverse to transfer from the active up into the passive tank, hence why a full flush and refill takes a while.
> 
> Regards
> D


Isn't the active tank the small heated one "up" in the engine compartment, and the passive tank the one "down" below the driver's seat?

At my last service, the service manager said that BMW no longer routinely flushes with every fill, but now simply "tops off" the tanks. I wonder if that procedure is required when there is no flush involved?


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## Kanuck (Feb 18, 2003)

According to Cummins (see here), the freezing point of DEF is 12F. That is quite a bit lower than what BMW says. In addition, the reason the urea concentration is 32.5% is to provide the lowest freezing point and so that as it thaws it stays in the same concentration.

It still seems to me that this could have been designed with only one tank with a heater that operated when the engine is on. It does not have to thaw the entire tank on startup. But, I am not a German engineer!

Still loving my 335d.


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## Penguin (Aug 31, 2003)

DnA Diesel said:


> The passive tank requires the car being being hooked up and the transfer pump run in reverse to transfer from the active up into the passive tank, hence why a full flush and refill takes a while.
> 
> Regards
> D


At my last service, the service manager said that BMW no longer routinely flushes with every fill, but now simply "tops off" the tanks. I wonder if that procedure is required when there is no flush involved?


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## Snipe656 (Oct 22, 2009)

I thought someone posted up a diagram on here that showed one port is for one tank and the other port for the other tank? Ports being the ones seen behind the little DEF door on the back fender of the 335d. I never have even opened that door so have no clue what it even looks like.


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## Snipe656 (Oct 22, 2009)

Do the other German car makers use two tanks too? Or really do any other car makers.


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## DnA Diesel (Jul 31, 2010)

Snipe, the tech noted the upper port was for the passive, but described the DEF flow as filling the active tank, and continuously reverse transferring the DEF backwards against regular flow into the passive tank. Not sure what the , my ETK/TIS doesn't have the LCI E90s onwards, so I can't actually see the procedure for myself. Perhaps someone has the specific procedure from the online TIS?

Penguin, the tanks are co-located underneath the trunk floor, where the spare tire used to be. (RealOEM diagram) The active tank is the one that the #1 actually points to, and it's kind of hard to see, but the upper/wider portion of the assembly is actually the separate passive tank. I don't know why BMW designed the two-tank configuration, or why they only heated one tank. :dunno:

Regards
D


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## dunderhi (Dec 10, 2006)

Penguin said:


> Isn't the active tank the small heated one "up" in the engine compartment, and the passive tank the one "down" below the driver's seat?
> 
> At my last service, the service manager said that BMW no longer routinely flushes with every fill, but now simply "tops off" the tanks. I wonder if that procedure is required when there is no flush involved?


I added DEF to both tanks via the ports.


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## Snipe656 (Oct 22, 2009)

I have not picked up my car yet but talked to them today and they found nothing wrong with the DEF system. Kind of seems like since my low fluid issue happened when the car was due for a yearly oil change that they did not see this as a problem so really put forth no effort on it. They had no real response to when I questioned why is it the car had a ton of fluid in it for the first yearly oil change but for the second yearly oil change it had next to no fluid within it. So will see if I manage to drive the car more this year and end up seeing if this happens again to me.


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## Penguin (Aug 31, 2003)

Kanuck said:


> It still seems to me that this could have been designed with only one tank with a heater that operated when the engine is on. It does not have to thaw the entire tank on startup. But, I am not a German engineer!
> 
> Still loving my 335d.


One technical reason might be that it takes less out of the battery to keep a small tank thawed, lessening load on the battery. The most likely reason, IMHO, is that the basic vehicle was not designed with a DEF system in mind, so to get the capacity they wanted, they had to split the capacity up into two places they could find space for tanks.

I wouldn't be surprised to see the two-tank approach disappear in the next major redesign, if Europe goes to a DEF requirement for passenger diesels.


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## TDIwyse (Sep 17, 2010)

dunderhi said:


> I added DEF to both tanks via the ports.


I remember your discussion on this. Did the passive tank fill take longer or have any different behavior than the active tank fill?


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## vadim_s (Apr 12, 2010)

MrBonus said:


> For anyone interested, they ended up replacing the transfer pump between the two tanks. This was the cause of my DEF warning coming on at only 5000 miles. I'm wondering if this is the cause of anyone else's woes as well. The dealer elected to pull codes when they went to refill due to the unusually low mileage of the required refill and that's how they isolated the problem.


Same thing happened to me at 8300 miles with a 2011 model. I printed out http://www.bmwtis.com/tsb/bulletins/bulletin_graphic_temp/b160310g.htm and asked them to pull the codes. The service advisor was pretty adamant about this being simply a low DEF issue and needing a top-off, but alas we were right and they replaced the pump as well


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## dunderhi (Dec 10, 2006)

TDIwyse said:


> I remember your discussion on this. Did the passive tank fill take longer or have any different behavior than the active tank fill?


I remember that I posted it in detail a while back, but I'm too lazy to look. Basically, I did the initial fill to clear the warning light and then another fill to top it off. If I remember right, the passive filled easily and the active was every slow fill the first time, but the active filled easily and the passive was every slow fill the second time around. I chalked it up to different states in the tank at the time of fill.

Anyway, I've put on 4,500 miles since I filled the tanks, and no warning light. So I would guess that my transfer pump is working, and my car was delivered in a less than full condition.


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## GoHamilton (Jul 30, 2007)

Well, fact is often times odder than fiction. I couldn't come up with this one myself. I drive about 100 miles a day so my mileage adds on fast. I got my 1000 mile warning and called my SA to schedule an appointment. It was in one week since I needed a loaner and I figured I should be ok (not having read this site for awhile). For the first time, I got the DEF reserve notice that I only had 200 miles left but I was bringing the car in the following day so I should be ok. At 1 or 2 o'clock after having dropped the car off at 7 AM I called my SA to see what was going on and she told me they had to drive the car for 20 miles. I was a bit taken and asked why. She said they topped off the DEF but the warning indicator was not going off. They drove it 10 miles and that did not turn it off so they drove it another 10 miles and it still had not gone off. Well, I picked up the car shortly after and now I only have 150 miles till the computer shuts the car off. The SA ensured me that they filled up the DEF and said that it may take several "cycles" before the light goes off. I was pretty fed up with all this and so I decided I would take the car. We will see if tomorrow brings a new day for me or if the light will still be on.


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## F32Fleet (Jul 14, 2010)

Penguin said:


> Isn't the active tank the small heated one "up" in the engine compartment, and the passive tank the one "down" below the driver's seat?
> 
> At my last service, the service manager said that BMW no longer routinely flushes with every fill, but now simply "tops off" the tanks. I wonder if that procedure is required when there is no flush involved?


Both tanks are located in front of the fuel tank in the rear of the vehicle.


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## 62Lincoln (Sep 26, 2004)

GoHamilton said:


> The SA ensured me that they filled up the DEF and said that it may take several "cycles" before the light goes off.


Wouldn't it be required to reset the car's computer when the DEF warning has been thrown, versus just relying on a reset? I would have guessed that the EPA wouldn't allow the manufacturers to set up the car to simply reset when a low DEF warning is thrown.


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## Snipe656 (Oct 22, 2009)

I am pretty sure more than one person on this forum has gotten the low light and they simply added some themselves and it reset. When I had the low light the dealer put some miles on it but no where near 20. My guess is what little they put on was from simply moving it to/from their storage lots that are not immediately next to the place.


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## GoHamilton (Jul 30, 2007)

Woke up this morning, started the car up and to my surprise, the warning was gone. I don't think they needed to reset the computer. I don't know what tank the car meters but I wonder if the delay was the time it takes the pump to redistribute the fluid as I'm guessing they just did a top off. We'll see though if I run out of DEF early this time around. I've had my car for a year now. My first DEF warning coincided with my oil change (which occured at around 11000). Since then though the SA has been off cycle as the following two times I had to bring the car in about 5000 miles after my oil change for a DEF top off. I even told him I wanted the DEF topped off with my last oil change but it did not happen. Next time I will have to be more adamant. That being said, I don't seem to have a problem with running out of DEF too early.


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## Snipe656 (Oct 22, 2009)

Not sure how true this is but I read that only one tank is monitored for it's level. What I'd wonder is did they top off both tanks and also if perhaps something is wrong with the tank transfer method.


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## dunderhi (Dec 10, 2006)

GoHamilton said:


> Well, fact is often times odder than fiction. I couldn't come up with this one myself. I drive about 100 miles a day so my mileage adds on fast. I got my 1000 mile warning and called my SA to schedule an appointment. It was in one week since I needed a loaner and I figured I should be ok (not having read this site for awhile). For the first time, I got the DEF reserve notice that I only had 200 miles left but I was bringing the car in the following day so I should be ok. At 1 or 2 o'clock after having dropped the car off at 7 AM I called my SA to see what was going on and she told me they had to drive the car for 20 miles. I was a bit taken and asked why. She said they topped off the DEF but the warning indicator was not going off. They drove it 10 miles and that did not turn it off so they drove it another 10 miles and it still had not gone off. Well, I picked up the car shortly after and now I only have 150 miles till the computer shuts the car off. The SA ensured me that they filled up the DEF and said that it may take several "cycles" before the light goes off. I was pretty fed up with all this and so I decided I would take the car. We will see if tomorrow brings a new day for me or if the light will still be on.


My light cleared in less than a mile after refilling. I think you may have a bad sensor or something like that.


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## dunderhi (Dec 10, 2006)

DEF Warning at 7000 miles Update

Well as the originator of this thread, and a guy filled both of his tanks himself I now have an update. At 12,200 miles my DEF warning light came on again. So, that's about 5,000 miles since the complete fill. If my transfer pump had failed, I would have only expected to make 3,000 miles on the active tank alone, so I'm not sure what's going on. Lucklily, I planning on getting 13K service next week, so I'll ask the dealer to take a look.


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## Snipe656 (Oct 22, 2009)

Hopefully they consider it an issue unlike the one I took mine into.


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