Diagnosis Help

oski · 03-20-2019, 02:00 PM

Hey fellas,

I'm trying to diagnose a lean DTC code P0171 on my 14' 435i. I did once receive a code for o2 sensor circuit slow switching from rich to lean for the downstream sensor. I have done a boost leak test and tightened down clamps on my chargepipe and other seals past the turbo outlet. The car does shudder at time when at cruising or low throttle situation. Car runs fine when driving hard. I replaced the MAF sensor so that should not be the culprit. I also cleaned MAP sensor with CRC MAF sensor cleaner. Below are the freeze frames from my OBD II app. Short term and Long term fuel trims are confusing me since I would thing the long term would be lower since the short term is negative. Only intake mod is a K&N filter in a mppk lower airbox (no mppk tune) Thanks for any help!

cfm56d7b · 04-09-2019, 10:56 AM

Is your car stock? Any modifications?

oski · 04-11-2019, 03:48 PM

Issue was resolved once I remove the MPPK lower intake box... I guess the stock tune doesn't like the extra airflow. Time for Bootmod3.

03-20-2019, 02:00 PM	#1
oski Private 15 Rep 53 Posts Drives: 2022 430i Gran Coupe Join Date: Oct 2017 Location: Austin, TX iTrader: (0)	Diagnosis Help - P0171 Lean Code Hey fellas, I'm trying to diagnose a lean DTC code P0171 on my 14' 435i. I did once receive a code for o2 sensor circuit slow switching from rich to lean for the downstream sensor. I have done a boost leak test and tightened down clamps on my chargepipe and other seals past the turbo outlet. The car does shudder at time when at cruising or low throttle situation. Car runs fine when driving hard. I replaced the MAF sensor so that should not be the culprit. I also cleaned MAP sensor with CRC MAF sensor cleaner. Below are the freeze frames from my OBD II app. Short term and Long term fuel trims are confusing me since I would thing the long term would be lower since the short term is negative. Only intake mod is a K&N filter in a mppk lower airbox (no mppk tune) Thanks for any help! Attached Images
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04-09-2019, 10:56 AM	#2
cfm56d7b Lieutenant General 5876 Rep 10,249 Posts Drives: 2017 440i Gran Coupe & 2015 X5 Join Date: Nov 2012 Location: Orange County, CA iTrader: (2)	Is your car stock? Any modifications?
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04-11-2019, 03:48 PM	#3
oski Private 15 Rep 53 Posts Drives: 2022 430i Gran Coupe Join Date: Oct 2017 Location: Austin, TX iTrader: (0)	Issue was resolved once I remove the MPPK lower intake box... I guess the stock tune doesn't like the extra airflow. Time for Bootmod3.
	Appreciate 0 Quote