2004 BMW 325i e46 OBD Codes P0174 & P0171

[dudley237]

Today I was driving and the Check Engine Soon light came on. I have an OBD sensor and hooked it up and ran the codes and it gave the results:

P0174 - System to Lean (Bank 2)
P0171 - System too Lean (Bank 1)

I have been looking at different forums as well as you tube and even the OBD Code results site to read about the issue and most of what I am seeing is the MAF or Mass Air Flow Sensor being defective. Most of what I have read has been for other models of BMW's such as a 2000 model or a younger model than what I have. I am curious if anyone out there has run into this issue.

Just another thing to throw in there. I have stock everthing. No K&N filters which I have read could cause problems if oil was mixed in with it. I am no mechanic but am willing to put in the hours and elbow grease to get something fixed. If anyone can help me understand what these codes mean or what to look for I would greatly appreciate it. Thank you

Scott

[hogsrul]

Had this recently and it was a bad DISA. Had to replace, got it from the dealer for $178. Not har thing to check. Very easy DIY.

[TacoEater]

Sorry, but what is a DISA....

[dudley237]

Anyone know what a DISA is?????

[Akcakoca]

I hadd same issue on my 2004'325i problem was a cracked hose i found it mechanic said throtle body and he said it coast 900$ from dealer i fixed it right nownits good no light

[dudley237]

Akcakoca, can you send me a picture of what you fixed?

[ReLiCaRiO]

I had those same codes. Then the maf code popped up, and lastly the cam position sensor. I changed the cps first, hoping the other codes won't pop up. I haven't gotten my hands on a scanner to delete the codes though.

[papasaund]

Two possible problems Mass air flow faulty and bad lower intake hose, between mass airflow sensor and intake manifold.

[harralk]

so how do you check the DISA?

[Lazerball]

I had the same problem onmy 325ci It turned out to be a cracked rubber ducting that connectsto the throttle body. Purchased a new one at www.bimmerspecialist.com , paid something like $18.00 dollars for it and replaced it myself. Problem gone and code reset.

[mrpickles]

I had these same codes on my 02 325xi e46. Found a leak in secondary air injector hose ($1.29 at advanced auto) which was the vacuum leak (this only is used during cold weather -- below 40). The damn thing was melted, dry rotted, and had completely collapsed. I also replaced fuel pump and filter ($250 for both on Amazon with 2 day shipping) problem gone and codes gone. Both very easy DIYs about 45min each at most. Indie shop down the street wanted $650 to replace both (that is if they didn't rip out my whole engine and air flow system looking for another vacuum leak that doesn't exist)

If you are having similar issues, definitely check the boot intake, especially the y valve first. Those are very common to go out. Also the MAF sensor on top of the air filter. Again, both relatively inexpensive parts and easy to replace.

[bens]

I had both P0171 and P0174 error codes for my 2004 bmw 325 ci
What I did checked for vacuum leaks and found one at the hose from CCV to the dipstick and replaced. Reset the code and it came back on so what i did took out the fuel injectors and cleaned them up. After reseting the codes again the same codes came back on. By the way i did forget to mention that I did clean the MAF sensor and also replaced the fuel filter without any success. After all this i went and ordered a new MAF sensor paid 139$ for it and installed. After reading the LTFT the came back down to a more normal reading from 12.4 to 4.2 . I take it problem solved although i have not driven the car yet i am confident that my problem is solved based on the LTFT reading. Bottom line check your MAF sensor when lean codes are triggering you service engine soon light.

[MRod]

I had the same thing and it was the boot at the throttle body.