[BeamerNooby]

Hello, I have a 2008 328xi Just recently on a cold start i got a check engine light and when i had it scanned the codes were: 29E0 and 29E1 mixture control and mixture control 2. Ive searched around but I can only find threads about the n54 and usually the guys have custom tunes. My cars bone stock no tune, it runs fine no rough idle, no misfires, no drop in gas mileage. I got the light cleared it stays off but after the car sits for a while 7-8 hours + the light comes back on same code but no affect to the driveability of the car. Any thoughts?

Note: this is the first time it’s happened. Somebody suggested it might’ve been the gas I used but i doubt that seeing as how i fill up at shell 91 always. Please any input would be helpful!

[Biginboca]

Since it’s for both banks it’s most likely a vacuum leak IMO. If one bank could be an O2 sensor.

You never get any rough idle?

[BeamerNooby]

Originally Posted by Biginboca

Since it’s for both banks it’s most likely a vacuum leak IMO. If one bank could be an O2 sensor.

You never get any rough idle?

No literally nothing, it starts up fine, idles fine, even at WOT feels the same no lack of power. Which is why I’m so confused could walnut blasting help?

[Biginboca]

Originally Posted by BeamerNooby

No literally nothing, it starts up fine, idles fine, even at WOT feels the same no lack of power. Which is why I’m so confused could walnut blasting help?

N52 doesn’t need walnut blasting, that’s a direct injection thing.

[BeamerNooby]

Ah I had a feeling this was going to be one of those annoying codes to figure out 😑

[Pladi]

Originally Posted by BeamerNooby

Hello, I have a 2008 328xi Just recently on a cold start i got a check engine light and when i had it scanned the codes were: 29E0 and 29E1 mixture control and mixture control 2. Ive searched around but I can only find threads about the n54 and usually the guys have custom tunes. My cars bone stock no tune, it runs fine no rough idle, no misfires, no drop in gas mileage. I got the light cleared it stays off but after the car sits for a while 7-8 hours + the light comes back on same code but no affect to the driveability of the car. Any thoughts?

Note: this is the first time it’s happened. Somebody suggested it might’ve been the gas I used but i doubt that seeing as how i fill up at shell 91 always. Please any input would be helpful!

My guess is your O2 (lambda) is not working properly or any of the other sensor used such as MAF, for mixture control.

Hows ur gas milage ?

[BeamerNooby]

Originally Posted by Pladi

My guess is your O2 (lambda) is not working properly or any of the other sensor used such as MAF, for mixture control.

Hows ur gas milage ?

I haven’t really seen a change in my gas mileage, it seems normal

[Pladi]

Originally Posted by BeamerNooby

I haven’t really seen a change in my gas mileage, it seems normal

regardless beamer boy its a sensor. Vacuum leaks have almost always erratic idles..

[BeamerNooby]

Originally Posted by Pladi

regardless beamer boy its a sensor. Vacuum leaks have almost always erratic idles..

Both my post cats o2 have been changed, so it’d have to be one of the pre cat o2’s? Looks like i’m going to try doing a smoke test

[Biginboca]

Have a look around your valvetronic motor gasket and valve cover. Sometimes a minor leak can occur which will throw a code but not show any other symptoms. If oil is leaking out then air can leak in.

I had a vacuum leak once caused from a leaking valvetronic motor gasket which also was leaking oil.

[Pladi]

Originally Posted by BeamerNooby

Both my post cats o2 have been changed, so it’d have to be one of the pre cat o2’s? Looks like i’m going to try doing a smoke test

Lambda means pre cat and those sensors are very different. Post cat O2 is just there for emissions . PRe cat its used for fuel calculations.

[BeamerNooby]

Going over to a local shop right now, they charge 89$ for a diagonistic lets see whats causing this strange code

[BeamerNooby]

UPDATE: so i took it down to a local bmw specialist, after a series of tests its determined that there are no leaks, everything was in check. His theory was there was potenial carbon build up which is causing the mixture code so he readjusted everything and put 2 bottles of Wurth fuel injector cleaner, and told me to drive it. Engine light has disappeared and car drives great so i’m hoping this has cleared my problem.

[gbalthrop]

Originally Posted by BeamerNooby

2008 328xi Just recently on a cold start i got a check engine light and when i had it scanned the codes were: 29E0 and 29E1 mixture control and mixture control 2...I got the light cleared it stays off but after the car sits for a while 7-8 hours + the light comes back on same code but no affect to the driveability of the car...

Originally Posted by BeamerNooby

...it starts up fine, idles fine, even at WOT feels the same no lack of power.

Originally Posted by BeamerNooby

Both my post cats o2 have been changed, so it’d have to be one of the pre cat o2’s? Looks like i’m going to try doing a smoke test

Originally Posted by BeamerNooby

Going over to a local shop right now, they charge 89$ for a diagonistic lets see whats causing this strange code

DTC stands for DIAGNOSTIC Trouble Code. That means it is supposed to HELP in Diagnosing a problem, NOT cause you to rush to spend money on a "perceived" problem (when your car is performing, running, idling just fine ;-) To "Diagnose" a problem, you have to: (1) understand what the code means, and (2) actually think about what different scenarios could cause it to be saved in DME memory. A code does NOT mean "replace part X."

1. WHAT the Codes MEAN:
WHAT Scan Tool or Software was used to read the two BMW Fault Codes: 29E0 and 29E1? Did the device/ software give a "Definition" of the Codes? Did anyone take the time to read Freeze Frame Data that indicates the mileage and engine conditions such as Temp, RPM, Load, etc. when the code was saved in DME memory?

BOTH those BMW FC's have TWO different definitions, EITHER too Rich or too Lean. Here are the Definitions found in Bentley:
P0171 | 29E0 | System Too Lean (Bank 1)
P0172 | 29E0 | System Too Rich (Bank 1)

P0174 | 29E1 | System Too Lean (Bank 2)
P0175 | 29E1 | System Too Rich (Bank 2)

So unless your scan tool/software gives you EITHER the correct Definition (Rich or Lean -- NOT just "mixture") or the corresponding P-code, e.g. P0171 for Bank 1 too LEAN, then you do NOT have all the diagnostic information the system can offer. INPA gives you BOTH a definition, AND the corresponding P-code, so you don't have to guess.

2. Possible Scenarios:
A) If BOTH banks are too lean, that would suggest a vacuum leak as has been suggested, but vacuum leaks usually cause a ragged idle, and even stalling at idle, and your car does NOT have those performance issues.
B) If one bank is too rich, and the other too lean, that suggests that the wiring harness connectors to the two "pre-cat" O2 sensors are switched. If the "post-cat" sensors were recently changed, or someone was working in that area who might have swapped connectors, that is quite possible.
C) Most any decent Scan Tool, even a $35 generic "stand-alone" tool that reads P-codes and Parameters, such as O2 sensor signals, can give you clues as to what signals the O2 sensors are sending to the DME.

In short, rather than spend $90 (plus "recommended parts & labor ;-) for someone else to diagnose a perceived problem, I would suggest:
1) Spend $35 or less on a Scan Tool such as one of these (depending upon whether you have a Windows Laptop or not):
https://www.amazon.com/Autel-AutoLin...+scanner+al319
https://www.amazon.com/ScanTool-OBDL...eywords=obdwiz

I have owned/used BOTH of those, as well as INPA, and for what you need to diagnose engine faults saved in the DME, either is good and easier to learn/use than INPA.

2) Take the car to whoever did the Post-cat sensors, and ask him to check if the pre-cat sensor connctors are swapped.

Please let us know what you find,
George

[BeamerNooby]

Another update: the light came back on and upon further analysis the tech said it looks like my 2 front o2’s need to be changed. He said their voltage is 2 which is too low.

Ive found someone selling 2 front o2 sensors brand new for e90’s for fairly cheap. My question is, is there a difference between the o2 sensors amongst the e90’s like N52, n54 etc., or are they all the same? Ive attached a pic of the o2’s.

[BeamerNooby]

Anybody? I could use some guidance before i make the purchase

[Pladi]

Originally Posted by BeamerNooby

Anybody? I could use some guidance before i make the purchase

Do some research on realoem site with part numbers. You want people to do the research for you ?

Find what car they were for, pull the numbers cross reference with you car.