Thanks for your replies.

Sorry I should have posted how I add the DEF….
The day we picked up our 2009 35d I purchased 2 of the half gallon “user” bottles of DEF. These small bottles have an automatic cut off valve built into the neck. The BMW parts guy suggested that once I used a bottle, I should cut a small hole in the bottom and use the auto cutoff feature to assure that I didn’t spill any DEF. It works like a charm. I just fill the user bottle from the bottom, screw it onto the DEF inlet(s), and push down to start filling the tank(s). Until recently I have only added DEF 2-3 times as part of normal maintenance (e.g oil changes). These fill ups took the expected 3-5 gallons for both tanks. But the recent 3 fill ups took less than half that amount. With the last one taking only a quart.


The problem...
I get a CEL and when I check the OBD I get a DTC of either P203 or 004BAC (depending on whether I use InCarDoc with an inexpensive OBD WiFI adapter or more recently Carly).

The first time it happened (last summer) I just added a little DEF, cleared the code and every thing was fine. When it didn’t come back, I forgot about it. But after two more CEL/DTCs, i”m worried that there is something wrong with the sensor that triggers the DEF code, even when the tank(s) are nearly full. I assumed that the DEF sensor would simply fail. But it looks like it may be still working, except in certain driving movements (e.g. tuning off a main road and heading down hill.).

I’ll check to see if our 2009 35d is still covered under the 10 yr extended warranty. Hopefully the dealer will accept the recent Carly Report as evidence of the sensor problem even if the CEL hasn’t triggered again.

Thanks again — Funf Dreisig


Edit: Thinking back…In all three recent CEL/DTC episodes I probably could have gotten the same result by simply clearing code. Adding the DEF was the equivalent of “whistling in the graveyard” — nice but not necessary.