2002 bmw e39 525i p0171 p0174 sytem too lean bank1 bank 2 help?

[ghost02]

Hi aim going pretty much crazy with my 2002 BMW e39 525i with 78k miles i have been getting these codes p0171 , p0174 system too lean bank 1 bank 2.
I have done pretty much everything and spent hundreds on dealers and repair shops any help would be highly appreciated i have done the fallowing repairs >

1.replaced all 4 oxygen sensors Bosch brand.
2.replaced air cleaner box.
3.replaced both air boots.
4.replaced ccv valve.
5.clean maf sensor.
6.used seafoam cleaner
7.car seems to run fine engine idles good not rough i always us highest gas so any ideas on what to do would be highly appriciated thanks

[ND4SPDLSC]

I just got the same codes, but I haven't started to troubleshoot it. I don't know why you would have lean on banks 1 and 2 though since you have an I6. Have you electrically tested the MAF sensor to verify that it is operating within range?

If the MAF tests good, then you could have a vacuum leak elsewhere like an intake gasket.

[producerbrasil]

Im in the exact same boat,

Here is my list if u go back in my threads u will see where i started at.

1. CCV
2. O2's
3.Plugs
4. Fuel Filter
5. Intake boot ( where the vacuum lines plug in )

I started running Lean and Rich, Now im running just rich. For my next step is gonna be new injector boots. only like 50 dollars shipped so hopefully that will help me out.

Have u misfired ?

[rathi60]

I just got the same codes, but I haven't started to troubleshoot it. I don't know why you would have lean on banks 1 and 2 though since you have an I. Have you electrically tested the MAF sensor to verify that it is operating within range?

If the MAF tests good, then you could have a vacuum leak elsewhere like an intake gasket.

+1

1st step is to rule out vacuum leak by doing a test. hope this was done before replacing parts. Cleaning a MAF sensor does not always work you may have to replace it. Test the MAF before repacing it.

[mattmartindrift]

fuel filter, vacuum leaks, those are my guesses.


ever check the ignition timing. have the Vanos seals been replaced?

[billzcat1]

My vote is vacuum leaks or MAF sensor. Happens all the time in VW-land and its allllllways the MAF or the intake boot.

[Poolman]

Back behind the intake on the driverside of the car are a number of vacuum hose's you can't see. You need to replace those hose's--they have probably never been touched and there's alot of heat back there to cause the hose's to break down.
You will need to remove the cabin air filter and duct work and use a mirror and flashlight to see whats going on back there. There are too many places that vac leaks can come from on these cars--sorry you wasted money on new 02 sensors--when they start going off --seldom are they bad--they are just trying to point us at what the real problem is

[pshovest]

Just went thru these codes on my '01 530i. DISA valve was leaking. A little bit of permatex form-a-gasket and all is well...15 minute repair. Cold weather seems to aggravate this problem. There are several posts on this and other Bimmer boards.

Paul S
BMW CCA 69606

Hi aim going pretty much crazy with my 2002 BMW e39 525i with 78k miles i have been getting these codes p0171 , p0174 system too lean bank 1 bank 2.
I have done pretty much everything and spent hundreds on dealers and repair shops any help would be highly appreciated i have done the fallowing repairs >

1.replaced all 4 oxygen sensors Bosch brand.
2.replaced air cleaner box.
3.replaced both air boots.
4.replaced ccv valve.
5.clean maf sensor.
6.used seafoam cleaner
7.car seems to run fine engine idles good not rough i always us highest gas so any ideas on what to do would be highly appriciated thanks

[slava837]

I had the same problem on my 2003 525I, 92,000 miles. It turned out to be vacuum leak in injector assembly diaphragm. Check for leaks by performing a smoke test on the system. Vacuum leak is the most likely cause of the p0171 and p0174 codes.

[Poolman]

What is a injector assembly diaphragm? I have never heard of it and would like
to find out just what this is. There are a number of spots that can wreck havoc
because of vac leaks--check the following
http://forums.bimmerforums.com/forum....php?t=1079942

[prophet540i]

Ive been having those codes for the past year or so I tried a whole bunch of stuff so I finally just gave up.. I cant get the car through DEQ but whateva ill trade it in eventually.. Thanks for bringing this annoying issue up.

[Poolman]

Ive been having those codes for the past year or so I tried a whole bunch of stuff so I finally just gave up.. I cant get the car through DEQ but whateva ill trade it in eventually.. Thanks for bringing this annoying issue up.

If your going through the vacuum leak problem on the 540 engine--the valley pan can cause alot of those problems --I don't have the 540
but have read on them some--that and around the throttlebody are the usual spots to look.

[prophet540i]

Yeah we have looked for leaks we sprayed the hell out of the whole intake manifold and air intake area, vacuum lines etc.. no change in idle or any change in RPM.. I ordered a CCV valve today to try that .. its only like 50 bux so yeah.. I was gonna put back my stock exhaust but decided to try to CVV first ..

[Redtallman]

check the temp sensor. Had that happen before,and come to find out my temp sensor was reading off the chart. So inturn it read as the motor was cold the whole time. So it never went thru warm up mode. change sensor all light went out all cat sensors and o2 sensor went back to normal.

[kerryb]

same issues with my i6.

[Gumbi4u]

Run a smoke test. Best way to diagnose this issue.

Kerry, My brother in law has a smoke machine down in middletown. Tell him "Ken" said to run a smoke test on your car. That machine will find stuff most folk wont.

[kerryb]

Run a smoke test. Best way to diagnose this issue.

Kerry, My brother in law has a smoke machine down in middletown. Tell him "Ken" said to run a smoke test on your car. That machine will find stuff most folk wont.

After unplugging my MAF the idle is fine... I was thinking maybe it might be the intake boot that has a slight hole or something.. dunno... was just going to go down to the stealer to get one and replace that..

I'll hit up that maniac if the intake boot isn't the problem...

[jamesdc4]

Kerry,

If unplugging the MAF and running the engine without it solves your idle problem, then you need to replace the MAF with a new OEM sensor.

Ken,

Nice sig.

[kerryb]

yeah, looks that way.. think i'll try a used one from bavarian auto recyclers for 50 bucks. see how that goes..

thanks all..

[kerryb]

Ken - the master found it in 5 min, was a hose behind the thottle body..

Send me a pm, there are a few things... Vanos, down here with fil?

Thanks...

[Jason5driver]

Spark plugs replaced?

[E39SB]

P0171 - System Too Lean (Bank 1)

P0174 - System Too Lean (Bank 2)

have the same car. the above post should take car of it

[keitho64]

I am getting an intermittent Bank 2 Lean but only when raining. I started a thread for that but reading through here I might as well try some of these ideas. Thanks for sharing all the ideas.

[champaign777]

same car same problem ... looks like related to 2001-2003 525 engines
2001 525i , today i got p0171 p0174 sytem too lean bank1 bank 2

all new staff , all new gaskets, no vacuum leak and engine runs excellent

MAF ???
If I unplugging MAF idle fails significantly - means it's ok ?

"After market oiled air filters foul the MAF" - i actually used some time K&N filter, but i cleaned MAF recently

[jamaica1]

Looking for information on the smoke test. I'm in NYC so anywhere in the vicinity is appreciated.

Val