# My 335D CBU cleaning up



## n1das (Jul 22, 2013)

I haven't had any CBU problems in my 535d or my X5 35d. They might have some CBU but I haven't checked. Power and MPGs are where they should be and no codes are being thrown. Both cars are always driven hard and like they were stolen and are seldom used for short trips.

My X5 35d had a good opportunity for some preventive maintenance to help minimize CBU. It recently got a long highway road trip at 70-80 MPH (and higher at times) from NH to FL. It was 22 hours of haulin' ar$e on the highway. The total travel time was 25 hours including my stops along the way. I was well rested before the trip and did the drive straight thru and was actually more wired than tired when I got to my destination. The return trip is coming up soon.

Worried about CBU? Give your car a long highway road trip!


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## Doug Huffman (Apr 25, 2015)

I too replaced a 2003 TDI ALH with an X5. 

When my TDI was nearly new, Uwe Ross minimized the EGR duty cycle. Some years later I had a preemptive IM exchange for a clean one (my guru's time saver). The original IM was lightly crudded. I never thought of it again. The TDI went to a new home in March 2015.


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## John Galt (Jul 21, 2012)

n1das said:


> Worried about CBU? Give your car a long highway road trip!


Bummer is that I drive 95% hwy and at "spirited" speeds, for 50,000 miles a year. My 2014 X5 35d had major issues with CBU. My "n of 1" proved that extensive, multi-hour hwy trips at high speed did not decrease CBU issues. Hopefully the 2015 I just bought will make my "n of 2" a 50% failure rate, and not 100%!


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## totitan (May 11, 2013)

Pierre Louis said:


> The very last version of the engine management computer (DDE), perhaps not just the update in software, was rumored to have addressed CBU. I know of no documentation on this except many felt the software "firmware" update lowered the mpg.PL


This is good to know PL. Now Im wondering if since my SCR system was replaced under warranty last year, and the EGR valve was replaced the year before, that perhaps I have the updated software/firmware and that my be why at 90,000 miles Ive had no CBU issues.

Another curious thing about my car is that since they replaced the SCR system the cars hardly uses any DEF....about a quart or less in 8000 miles last time I checked.

I also wonder if since my car was owned by the dealer for at least two years if they may have done some reprogramming to the ECU to minimize the EGR valve opening :dunno:


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## Pierre Louis (Oct 23, 2011)

I do know that the part number for the DDE kept changing from 2009 to the end of the NA run through year 2011. That tells us something.

PL


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## Flyingman (Sep 13, 2009)

I'm almost at 100k and still no CBU. I've had my doubts many times but the car keeps pulling adequate MPG, Power, etc... I'm sure it could probably use a cleaning by now.

I have noted that my car has settled down a lot the last year with almost no nuisance issues. Perhaps it is in it's sweet spot!


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## G335d (Apr 22, 2014)

Update to post #14:

Dealer has had my car for a week now. Both the Regional Tech Rep and BMW NA are involved, my dealer SA is doing a good job of getting them to work on my behalf. I'm told by BMW NA that the triumvirate is working on "helping" me with the costs of the CBU cleaning performed a couple of weeks ago and the current issue with the red light warning about the "incorrect def" being in the car. We shall see what that means.

In looking at the def, the SA states that it had high water content, and also that they couldn't fully fill the active tank. That explains why I was only getting 6000 miles after a def fill up. Thankfully they were the ones filling the def the last few times, so they can't say that I put non-BMW def in the tanks. It sounds like they are having a hard time putting all of these pieces of the puzzle together, despite the fact that I keep (nicely) pointing out that these are all issues that many other owners have already experienced (thanks to these forums for the shared information!)

In the meantime I have an X3 28xDrive for a loaner. Nice driving vehicle, but I'm no fan of the 2.0 engine in any of the platforms I've driven. Particularly the Honda/Toyota sound at idle . . . Nothing wrong with those cars, but I expect more from a $55,000 vehicle I guess.


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