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DEF Warning at 7000 miles

13K views 104 replies 25 participants last post by  Snipe656 
#1 ·
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.
 
#51 ·
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.
 
#52 ·
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.
 
#55 ·
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.
 
#56 ·
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
 
#57 ·
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?
 
#58 ·
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?
 
#59 ·
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
 
#60 ·
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?
 
#61 ·
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.
 
#68 ·
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.
 
#63 ·
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.
 
#65 ·
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
 
#67 ·
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.
 
#72 ·
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.
 
#74 ·
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.
 
#75 ·
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.
 
#76 ·
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.
 
#79 ·
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.
 
#82 · (Edited)
I had my 13,000 mile service today and the verdict is that the transfer pump had lost its prime. The passive tank was 100% full. What is surprising is that I travelled 5,000 miles on the active tank before the warning light came on.
 
#84 ·
The SA didn't say how he knew, but he did mention that the system threw a code and needed to be reprogrammed. :dunno:
 
#85 ·
Well, it's only been two weeks now since my last post and my DEF warning has come on again. That's only about 1200 miles since my "top off." I suspect I also have a pump problem and they may not have filled my tank up completely. Regardless, if my SA does not seem to be knowledgeable or helpful, who is the next best person to talk to? Who do I escalate this with if I need to? Thanks.
 
#88 ·
My DEF warning just came on today at 4623 miles.

This is after the car was serviced by the dealer with about 1000 miles on it for a SES warning related to the DEF valve.

BMW really needs to get this DEF issue sorted.
 
#92 · (Edited)
The sad thing is that it may just be simple "dummy switch". I dunno if there's actually a gas tank type of measuring device like a float in the tank. It sure would be nice if you could see the level in the dash display like you can with the 328/335s oil level check.

So far it seems the majority of DEF problems (other than being inadequately filled at PDC) are in the northern climes. Maybe it's the freezing def problem?
 
#102 ·
DEF Warning at 9300 KM



Taibani please see my post in other string. We have the same issue with 100% Passive full and low active. Mine will be fixed under warranty as was top up of active tank. I am sure that they came to this conclusion based on a code identified in you Special Service Bulliten.
Cheers:rofl:
 
#91 ·
Def Warning at 9.3K KM

Mine goes into shop on Friday this week. Will attempt to get them to pull codes re pump activity between tanks of DEF.
Look forward to receiving copy of SB. This is a issue that 335d seems to have that needs to be dealt with by BMW from a maintenance/warrenty perspective.
I will report my experience with the SA on this issue when I get my car back.
 
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