BMW P0171 & P0174 System too Lean How to Diagnose & Repair Smoke Test Crank Case Pressure and MAF

This E46 came in with DTC's P0171 & P0174 codes for lean running engine. I go thru some of the common areas to test and how the MAF readings led to finding a plugged up air cleaner E39 E53 383 X3 X5 Z3 Z4 E60

[@alfrednavarro2391]

Awesome video! I've been experiencing lean codes for several months and could not figure it out. I checked my MAF for the readings you showed, and sure enough, my MAF was the culprit. Thank you for your simplistic explanation of a common problem. No more lean codes for me and my E46 is running great!

[@ripsgarage]

Thant's awesome!

[@negritorican]

Thanks for making this video....all the videos on youtube showing this E46 is always the intake boot being cracked. Common problem in the E46. Good to see other diagnostics for the same codes.

[@ripsgarage]

You're welcome!

[@StevenPerez-ge9ch]

​@Rip’s Garage I replaced everything under the hood vacuum lines intake boot cleaned everything ccv new etc everything new I'll try the new air filter and see thanks for the video

[@tkajtsai1586]

Same 0171 0174 codes were on my 2001 E53 X5 3.0i , I replaced every possible parts and finally it fixed. The real cause was on fuel injectors . Very possible were those O rings on them. I don’t want to take any risk. Simply replace them all with new ones. I used ADO oem parts. Genuine BMW too expensive.

[@ripsgarage]

Good job man!!

[@StevenPerez-ge9ch]

By the way thanks for this video it just fixed my codes i couldnt figure it out 😂 everything is new except the air filter thanks the one and only video on youtube

[@ripsgarage]

That's awesome man! Thank you!

[@bilalhaidar3]

Thanks for sharing!!! Really so professional!!!

[@ripsgarage]

your welcome!

[@mikeault7]

I replaced my MAF still clean lol . Thank you for the video

[@ripsgarage]

Awesome job man!

[@pedrolopez3954]

i just got e46 and i got these two codes and bad idle. i have changed coil pack and spark plugs, intake boots look good. change secondary air injection pump and valve and still getting these codes and a brand new maf sensor. BMW came with a cold air intake. could that be the culprit? i also heard the disa gasket but can't get in there since both bolts came also stripped. what would your suggestion be?

[@ripsgarage]

It's tough the cold air intake could be affecting the MAF readings. This usually happens if there is air leaks between the MAF and intake, and if the MAF mounting to the air cleaner has been modified. But before heading that direction, have you checked the Crankcase Vent Valve? Or when it was last replaced? Those hoses along with the valve fail all the time.

[@pedrolopez3954]

Not yet but i will. I will do a smoke test then tonsee if there is any rips on intake hoses and if it leaks through thr disa . Thanks for your reaponse

[@jonredd650]

Awesome!

[@ripsgarage]

Thanks!

[@airwolf12999]

Good video with some great tips and info it will come in handy with a 03 e46 project i picked up, also i gotta say i cringed when you started knocking the crap off the air filter above the dip stick tube will the dip stick missing..

[@ripsgarage]

Holly Cow! I didn't even notice that!! Good catch!!

[@airwolf12999]

@@ripsgarage was a yikes kind of moment.

[@likits1999]

Awesome diagnostic. I have a P1092 bank 2 lean code on my 2001 330i and haven't been able to find that much info on it. Have you had that code before? I'm gonna replace my air filter just in case. Thanks so much in advance.

[@ripsgarage]

P1092 is a slightly different DTC for lean condition. Similar testing process by monitoring STFT and LTFT on both banks. It's usually a faulty upstream oxygen sensor. I believe both bank 1 and bank 2 oxygen sensors are the same exact part number on this engine. I would mark for identification and swap one sensor over to the other bank. Than disconnect the battery overnight or use the battery cable shorting method to reset the DME completely, which in turn resets fuel adaptations to 0. Than drive the car and when the MIL returns, see if the DTC moved to the other bank, P1090. That will confirm Bank 2 sensor was faulty and when moved to Bank 1, set the corresponding DTC. Hope that helps. If not, definitely follow some of the tips in the vid for checking on a lean running engine!

[@Ct6v0tk88]

Hi thanks for sharing your experiance with us, i have e39 m54 engine, p0174 and p0171 popping at the same time, i have no vacuum leak, new 02sensors, new ccv, new vcg, fuel pressure is 51, car runs great on highway and in city,but shakes on low rpm(idle 650) what else should i try?how do i get rid of codes? please help.THANKS.

[@ripsgarage]

Hi, do you have access to a scan tool? If so are your fuel trims high at idle upwards of 20%? Are you able to smoke test the air intake?

[@Ct6v0tk88]

@ripsgarage thanks for reply, I do have scan tool yes, I did smoke test by Appling smoke in to maf tube, but did not see any leaks, when I opened the oil refill cap lot of smoke came out with the pressured air, I am guessing there is no leak.

[@Ct6v0tk88]

@ripsgarage my short fuel trim sensor 1 is 27.2 and sensor 2 is 99.2 on idle 750 rpm

[@ripsgarage]

@@Ct6v0tk88 Sorry for late reply, not getting the notifications. What about your MAF grams/second? On wide open throttle?

[@Ct6v0tk88]

@@ripsgarage 158

[@enriquetorres5626]

Can you please give us the links of the equipment used in your video? I am interested in purchasing them

[@ripsgarage]

Sorry for the late reply, the scan tool is not available. I work with Innova Electronics when they were developing that tool, is how I came to have one. However, Innova's 5610 model on amazon, has the same functions and more. Here is the link to that one. Definitely a great tool to have for any car your working on! www.amazon.com/5610-Bidirectional-Lifetime-OE-Level-Functions/dp/B07Z481NJM/ref=sr_1_1_sspa?crid=27MCXE1WKNSV6&dib=eyJ2IjoiMSJ9.5OuLx6wXvy-8fCMsPPDJXy8NVYwzmdLSePW6_YgDFfr-OVuQw1AHu30E78snIF-7xReHXKK9oGEFgN6nzx52rDHZn_AwomuWftYTp8FEy0xGcm-54L2oCJyzUnqxEENgYCvNxA2xhnHSYiPpi5n5GZWgYEb6MzI4RhiT_kQDPxx9TFBn8Tr78467lGK6Q8jDsl4edhTCn47hutu6xaDD-w.cP5iz0tR_VDJB0S5hwhV2nE_qxwhh-P1Jfy3zpcko0M&dib_tag=se&keywords=5160+innova&qid=1709340857&sprefix=5160+innova%2Caps%2C130&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&psc=1

[@RandomRubio]

Did this fix their code?

[@ripsgarage]

Hi there, yes it did! A few reasons on the E46 for lean conditions. But get an inexpensive scan tool like the Innova 3160 or 5160 and you can read the MAF g/s (grams second) if your not reaching the spec on wide open throttle, than remove the air cleaner and go drive it. If it's still the same, replace the MAF. If the g/s are good, smoke test and crankcase test and fuel pressure/volume test it.

[@RandomRubio]

@@ripsgarage I’ve been chasing these two codes on my 2005 x3 e83. Replaced 02 sensors, the whole ccv system, intake boot, disa valve o ring. Still get the code. I saw ur checking the fuel on the scanner, my range is around 14 and 16 as well. Also my maf is around 4.5 g/s

[@RandomRubio]

Sorry, I have 16-20% positive long term fuel trim and negative 5 -8 % short term . Not sure what to make of this data tho.

[@xepiicxalexs]

@@RandomRubio did you figure out ur issue I have a 04 x3 e83 6 spd having the same issue . I’ve replaced the valve cover gasket , pcv , brake booster hose , disa vavle , fuel pump and regulator , 02 sensors and cats still fighting for my life and the smog is coming up in a few months 😢

[@RandomRubio]

@@xepiicxalexs did u try replacing the rubber intake boot and maf sensor

[@gxddxxg6089]

Just bought 2004 bmw 3 series and I went to auto for diagnostic test Said MAF AND/OR P0171

[@ripsgarage]

Definity a lean condition code, look at your MAF grams/sec on wide open throttle! Also, for air leaks after the MAF sensor to the intake.