4BCC - DDE: Reducing Agent Passive-tank fill-level sensor signal

[Best4x4xFAR]

So one of the few 'Present' Codes right now per the Foxwell Scan is this 4BCC. I've found multiple threads about the code, and the associated 'full' sensor on the passive DEF tank. I've cleared it and it comes right back.

Seems it is fairly common for it go bad, and I've also seen 'fixes' that include a VW sensor replacement (though I'm not clear on the details), and the 10 Ohm resistor across the contacts that essentially tells the system the tank is always full I would assume (no?)..

It seems clear that the sensor is not available as a replacement part, and that BMW insists you buy the whole tank for replacement.

Not clear what the function of this sensor is, and what the side effect is to the systems to basically bypass it with the 10 ohm resistor trick. So if anyone knows and can fill me in, that'd be great..

Also, anyone know from experience if this is covered under the 10 year/120k CARB states extended emissions warranty?

[e70x5d]

the sensor when functioning properly reads 10k ohm ,so when sensor fails no longer reads the required resistance. Here is a great write up that doesnt require removing the tank and shows how to test which sensor is at fault. amazon has a 100 pack of the resistors for $6 with prime. im on my 3rd day with out a CEL. Good luck.

https://www.bimmerfest.com/forums/sh...=667126&page=8

[Best4x4xFAR]

Originally Posted by e70x5d

the sensor when functioning properly reads 10k ohm ,so when sensor fails no longer reads the required resistance. Here is a great write up that doesnt require removing the tank and shows how to test which sensor is at fault. amazon has a 100 pack of the resistors for $6 with prime. im on my 3rd day with out a CEL. Good luck.

https://www.bimmerfest.com/forums/sh...=667126&page=8

Thanks for the link! I've read many threads on the subject, but somehow missed that one. I at least understand now that the 10K ohm resistor doesn't bypass the level reading, just the circuit's integrity check (I guess that is an accurate description)..

It appears from BMW Reimbursement Program Website that the Passive tank is covered in the extended warranty on my VIN (it was originally registered in a 'CARB State' (and still resides in a CARB state).

Now I have to decide whether I feel like gambling on what else will be wrong after the dealer monkey's get their hands on it..

Or if I want to try the PIXLFIX fix.. LOL!

[crystalworks]

Bosch sells a kit now. No need to use VW parts anymore which aren't a100% likeness. I just installed it in the wife's x5 and no longer have any level sensor or heater codes. Not cheap, got it at fcp for north of $250 but it's cheaper than buying a tank.

Originally Posted by Best4x4xFAR

So one of the few 'Present' Codes right now per the Foxwell Scan is this 4BCC. I've found multiple threads about the code, and the associated 'full' sensor on the passive DEF tank. I've cleared it and it comes right back.

Seems it is fairly common for it go bad, and I've also seen 'fixes' that include a VW sensor replacement (though I'm not clear on the details), and the 10 Ohm resistor across the contacts that essentially tells the system the tank is always full I would assume (no?)..

It seems clear that the sensor is not available as a replacement part, and that BMW insists you buy the whole tank for replacement.

Not clear what the function of this sensor is, and what the side effect is to the systems to basically bypass it with the 10 ohm resistor trick. So if anyone knows and can fill me in, that'd be great..

Also, anyone know from experience if this is covered under the 10 year/120k CARB states extended emissions warranty?

[josiahg52]

I've heard of issues with the active tank and the various non-sanctioned repairs. The active tank is covered by a BMW extended warranty. I've not heard much about the passive tank. My active tank was replaced at 118k miles free of charge by BMW.

[crystalworks]

Sorry. Completely read over passive tank.

I have no experience with that particular failure... Yet.

[e70x5d]

Nice problem solved, my vin doesnt come up with passive only active what the heck.

[Best4x4xFAR]

Originally Posted by e70x5d

Nice problem solved, my vin doesnt come up with passive only active what the heck.

Suspect it has to do with the original state the vehicle was registered in? My understanding is that vehicles registered in states that adopted the California Air Research Board (CARB) emissions standards have additional extended emissions warranty coverage. Maryland was one of these states..

Of course it will be just my luck to go to my dealer, and have them say its not covered..

[josiahg52]

Everyone seems to think that the CA emissions warranty is super-duper warranty that covers everything.

First, there are two federal emissions warranties. 2yr/24k mile coverage for ANY part that causes a FAILED emissions TEST. Then, an 8yr/80k mile warranty that covers catalysts, ECU and parts of the OBD system.

The CA warranty is 7yr/70k mile warranty covering SPECIFIC "high cost" emissions "related" components. CA provides this list in one of the CARB manual sections. The vehicle manufacturer determines what "equivalent" systems and parts are covered. For example, the X5d doesn't have any traditional vapor recovery system but does have an active NOx reduction system with SCR.

It's not a magical warranty, It's not a forever and everything warranty. Definitely try it if you can and maybe you can get some relief.

The active tank, NOx sensors and FRM were all covered by a BMW extended warranty to 10yr/120k miles. My urea dosing module was also replaced under this warranty. I had heard that some passive tanks were also covered but the two letters I received only covered the three items I mentioned first on my vehicle. I also heard some EGR coolers were covered by an extended BMW warranty. I was not so lucky although a bracket or some piece of it was replaced under a recall order.

[Best4x4xFAR]

Put 2.5 gallons of DEF into the Passive tank this weekend. Don't think it filled it, as it all went in, but the Code has changed to not present when I run a scan with the Foxwell. Been three drive cycles since filling, have to wait and see if it comes right back or not..