[supermann125]

I've got a 2011 335d with 49k miles. Is there anyway I can have the dealer check for CBU without any codes or diminished performance? It's CPO, so I've got the power train warranty out until 100k

[kbsilver]

They can pull the EGR valve and look in with a boroscope. But what's the point of doing so? Without an SES code they will not do anything under warranty and even that check would be on your dime. Based on trending, the average point of needed CBU cleaning is a little over 50K miles so will likely happen soon enough for you.

If you are reading the boards you know at least they have a pretty good handle on detecting and cleaning (preventing probably not so much). Most likely you will pop an SES for an injector at minimum adaptation value. This often has nothing to do with an injector but is the CBU.

[m80theWolf]

I've tried various ways of asking them to look for it with three different CA's, and the above post is right - no ses, they won't waste their time. I'm in the same boat as you, cpo, but I also bought the maintenance plan at purchase

[Vreimann]

Originally Posted by supermann125

I've got a 2011 335d with 49k miles. Is there anyway I can have the dealer check for CBU without any codes or diminished performance? It's CPO, so I've got the power train warranty out until 100k

With very few tools and some time 1-2 hours you can have a look yourself.

I'm certain now there are enough threads and instructions on how to get those pieces off to take a peek.

[Got_Diesel]

61k miles, no CBU for me...yet

[kbsilver]

Originally Posted by Got_Diesel

61k miles, no CBU for me...yet

Mine was 100% issue free until it popped the SES at 53K. Only clue was my MPG was definitely down at least 10%, which has been restored with the CBU cleaning.

[Got_Diesel]

Originally Posted by kbsilver

Mine was 100% issue free until it popped the SES at 53K. Only clue was my MPG was definitely down at least 10%, which has been restored with the CBU cleaning.

yeah, i've been getting 29-31mpg when i used to get 21-33mpg so I'd say my mileage is down a bit. No SES yet. Once in a while I get a rough idle which makes me a bit worried. I also remember a bit more power back in the day. If a carbon cleaning brings those things back i'd be happy. If my dealer covers it under warranty, even better!

[kbsilver]

Originally Posted by Got_Diesel

yeah, i've been getting 29-31mpg when i used to get 21-33mpg so I'd say my mileage is down a bit. No SES yet. Once in a while I get a rough idle which makes me a bit worried. I also remember a bit more power back in the day. If a carbon cleaning brings those things back i'd be happy. If my dealer covers it under warranty, even better!

Yep, sounds as you will be due pretty soon. For a 150 mile leg highway trip with no ac, traffic or regen I was able to exceed 42 MPG. All the subtle issues were cleared up to be like new once CBU was cleaned. It even has more of the "growl" sound I remember it use to have. I am guessing that all the CBU in the intake dampened/muffled the growl. If you have a warranty it should be covered.

[remlemasi]

I've just hit 70,000 with no CBU yet.

Bought the car at 44,000 in March, 2013. CPO expires in March, 2017, which is right around where I'll hit 100,000.

Sounds like CBU is inevitable, but I'm wondering why it hasn't popped up yet. Will it always trigger an SES? Is there a possibility that I will drive around for the next 30,000 with massive CBU but no SES?

What are some typical codes thrown for CBU?

(I did have SCR tank replaced at around 65,000.)

[kbsilver]

BMW will not cover any CBU cleaning until the SES goes on. In my case the only code was for Injector #2 minimum adaptation limit. Some hard driving cleared the SES, but when checked by the dealer still had the CBU cleaning. Although in my case the code was for an injector, it was caused by the CBU. No injectors were ever replaced on my car.

[GottaBeKD]

56k km here.
New injectors. Check
New throttle body. Check
New DDE. Check
Carbon blasting. Check.

[remlemasi]

Originally Posted by GottaBeKD

56k km here.
New injectors. Check
New throttle body. Check
New DDE. Check
Carbon blasting. Check.

Ah! And I should clarify I am at 70,000 miles!

[9mmkungfu]

If you guys want to check for carbon build up, read this thread here:

http://5series.net/forums/diy-do-you...-engine-53457/

[eurojulien]

my mpg seems down. I really have a hard time getting over 30ish mpg lately. no ses though other than scr tank level sensor (bringing her in next friday for that).

2011 335d 53k miles

[kbsilver]

53K miles is exactly when I popped the SES on my 2011 D that resulting in CBU cleaning. The SES was for injector #2 minimum adaptation limit reached, although no injectors were replaced, just the carbon cleaning. My car had zero issues other than being down on MPG before the SES went on.

After cleaning MPG came back (did 42mpg on a 150 mile highway stretch), engine was a little more responsive, and the diesel "growl' was back. Apparently it's muffled somewhat by the carbon.

[ingenieur]

Try to very slowly lift the engine speed while stationary in park - but not over 2000 rpm. If the engine feels a bit rough or starts to feel nervous at 1800 - 1950 rpm then this could indicate the ports are sooted.

[BB_cuda]

Originally Posted by Got_Diesel

61k miles, no CBU for me...yet

did you look or just no diminished performance/lights yet?

[bdwyer]

Originally Posted by ingenieur

Try to very slowly lift the engine speed while stationary in park - but not over 2000 rpm. If the engine feels a bit rough or starts to feel nervous at 1800 - 1950 rpm then this could indicate the ports are sooted.

I'll second this, try holding each 100 RPM mark and feel for stumble. I'd suggest music and HVAC off for this process. Mine was slightly rough at 1100 or 1200 rpm if I remember correctly. Just had the CBU cleaned up and now its silky smooth.

[remlemasi]

Originally Posted by bdwyer

I'll second this, try holding each 100 RPM mark and feel for stumble. I'd suggest music and HVAC off for this process. Mine was slightly rough at 1100 or 1200 rpm if I remember correctly. Just had the CBU cleaned up and now its silky smooth.

Performed these informal tests and absolutely no roughness.

71,500 miles and counting, no CBU!

Although I did start getting 4D16 (DeNOx System Inefficiency) and 4D35 (Reducing Agent Metering Valve, Plausibility) codes, for which SES light comes and goes. Are these hallmark signs of impending CBU?

[BB_cuda]

remle, i would say those code descriptions sounds more like DEF/SCR system. I would first perhaps look at the metering valve and see if it needs cleaning right where it bolts onto bottom of DPF. Use distilled water. I am guessing but have read here of folks' metering valve getting crystallized and clogging.

[Mik325tds]

Originally Posted by remlemasi

Performed these informal tests and absolutely no roughness.

71,500 miles and counting, no CBU!

Although I did start getting 4D16 (DeNOx System Inefficiency) and 4D35 (Reducing Agent Metering Valve, Plausibility) codes, for which SES light comes and goes. Are these hallmark signs of impending CBU?

The fact that you don't have the correct DTCs for CBU doesn't mean you don't have CBU. I bet you have CBU. The question is how much. My car was at 97k miles when I pulled the intake and performed the cleaning. I had no codes at all but considerable CBU.

[kbturbo]

Just dropped mine off at the dealership tonight. Had an insufficient egr flow detected code. Still under cpo. Light came on at 50,300 miles. After driving the 2015 X1 loaner car home, I'll be happy to have mine back