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  #1  
Old 04-13-2009, 08:59 PM
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P0171, P0174 resolved

Hi Everyone,

About 4 weeks ago, my service engine soon light came on (2003 X5 3.0i). I had the codes read and found P0171, P0174 indicating both banks were lean. Anyone who has had to do the search for these codes knows there are many reasons and lots of things to try. In my case it was a failed DISA valve which was causing a vacuum leak. As is always the case, this was the last thing I tried in a long list of replacement parts. In any case, I wanted to give some details which I would have loved to have found when I did my initial search. Here is what I did:

1) I purchased a CarChip to read the engine codes and reset the SES light. For those of you who haven't seen this device, its an OBDII code reader which plugs into the port and monitors on a 5 sec interval storing a variety of engine information. This was useful not only to reset the codes, but also to see the readings from the O2 sensors and the lean condition on the fuel trim.

2) I searched for vacuum leaks. Apparently the most common location for this problem is the elbow just after the MAF sensor. Mine checked out fine, and I didn't hear any vacuum whistle.

3) I cleaned and eventually replaced my MAF sensor. I didn't see much of a change after cleaning, but it was clear that the engine ran smoother when the MAF was disconnected. So I decided to bite the bullet and replace the MAF. I bought a new Siemens OEM replacement from RAeuropean (http://www.rmeuropean.com/). SES light remained.

4) I replaced the fuel filter. There are several good DIY on the net for this. My only trouble was removing the fuel lines, for my X5 (2003) they had a couple of slip on connectors with green clamps to keep the connectors from slipping off. There were no hose clamps. SES light remained, although between this and the MAF I think I picked up 1-2 MPG.

5) After a more exhaustive search for a vacuum leak, I heard a whistle from the DISA valve (also called the adjuster unit:11617544806). After a more extensive web search, I realized I should have checked this first. It is easy to remove, just 2 T40 torx bolts, then it pulls out from the manifold. When you pull it out, you should see a valve.
In my case, the valve was only connected to the box on one side, the lower pivot point had broken entirely. This allowed air to enter the manifold (after the MAF) - apparently this is not uncommon. In fact the original part number up to 04/2004 has been retired. After a short trip to the dealer (and ~$212) I was back in business with no SES light. I also watched the long term trim readjust with driving (using the CarChip). After a couple of hours of driving, the long term had decreased considerably.

In the end, I'm happy that I replaced the MAF, Fuel Filter, Air Filter, and I even did a set of plugs as I am now just over 105,000, so many of these lifetime elements are probably close to EOL. I also saw a jump in MPG.

I hope this might help someone else when confronted with these lean codes...If I were to do things over, I would first check for leaks (5 minute job), then pull the DISA (10 minute job), then clean/replace the MAF (15 minute job), and only as a last resort work on the fuel filter (2 hr job).
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  #2  
Old 01-07-2010, 04:13 PM
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Oh how I wished I would have read this earlier. I replaced everything you spoke of, plus four new O2 sensors, only to discover it was a leaky DISA. Still, with all the new items (which needed to be replaced anyway), I should be good to go with the new valve when I put it on tomorrow. Thanks for at least confirming I am mostly sane.
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  #3  
Old 03-30-2010, 10:19 AM
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Is there a DISA valve on the m62 V8 engine? I'm getting P0171 and P0174 codes and they come back after resetting them.
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Old 03-30-2010, 08:42 PM
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I can't say for sure, but would think so. It should be located between the Mass Air Flow Sensor (attached to the air filter) and the air intake on the engine. the only way the shop could find my problem was with a smoke test that injected smoke into the intake system and the look to see if/where it leaked. Good luck!
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Old 03-31-2010, 08:44 AM
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Nodef, do you have pictures of the DISA valve location? My SES light popped on and I read those same two codes. I was planning a fuel filter change and MAF cleaning, but this sounds like the culprit. How much is the part? Available through internet or bavauto or is it just a stealer item?
Thanks!
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  #6  
Old 03-31-2010, 01:07 PM
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Part#7
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2006 X5 3.0L - Schwarz Black/Truffle Brown
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Old 03-31-2010, 02:50 PM
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Thanks Wayne. My 328iC sounds like a diesel- gonna check that car as well. Found this part for $168 cheapest I've found.
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Old 03-31-2010, 03:30 PM
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Yeah if you're getting that hollow rattle sound, it's probably broken. Check inside the manifold for any missing pieces. Most times, the vacuum leaks that result because of the DISA, isn't necessarily the DISA itself but more or less the seal around the DISA. On my '06 3.0, it's a round red rubber gasket. You can choose to replace just the gasket or reinforce it possibly using a gasket maker.
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Old 04-06-2010, 04:29 PM
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Great post. I just got these two codes on my 2001 4.4i last weekend. Nothing crazy, but I don't drive my X5 much at all as it's a secondary vehicle (maybe twice per month, sits in the garage all year). I haven't noticed any change whatsoever in performance or gas mileage, so I'm wondering if anyone noticed any changes in engine behaviour just prior to discovering the check engine lamp?
I'm thinking if it's going to be a shot in the dark going through all of these parts, I may as well just bring it to the dealer as it may be cheaper for them to replace only the part that's required than for me to spend all of this cash on trying different stuff. Even $168 USD is a lot if it's not going to guarantee my problem will be solved.
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Old 04-06-2010, 08:41 PM
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Its not hard to check if the DISA valve is broken. Just unscrew the 2 torx screws and unplug the connector at the top of the unit. Pull the unit out from the intake manifold and look at the flap. Here's what a broken DISA valve usually looks like.

Flap Loose but still in place
Pieces that broke off which hold the flap in place and rotates the flap open and closed.

Close up of broken part.
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