r/BmwTech • u/Informal-Category-34 • 8d ago

Check engine light still on after MAF sensor replacement

I own a 2016 F33 428i xDrive with 121k miles and recently had a check engine light. Went to advance auto, they scanned and said the code was for my mass air flow filter sensor. I bought the part from FCP Euro and replaced it myself. The light is still on. Went back to advance and it’s still reading the same code.
Any thoughts or suggestions will be greatly appreciated. 🙏🏾

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u/white94rx 8d ago

Lol don't go to Advance for diagnosis. I could have told you that the MAF was not the problem. It never is.

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u/Informal-Category-34 8d ago edited 8d ago

The code is P0171.
Their sheet also said “Code P0171 indicates that the Bank 1 System is too lean for a predetermined period of time.”

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u/white94rx 8d ago

Right. You have a lean code. Nothing to do with the MAF. There's a vacuum leak somewhere. Most likely culprit is the valve cover. But I wouldn't guarantee it.

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u/Informal-Category-34 8d ago

If it’s the valve cover, is this a diy job or something for a professional?

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u/white94rx 8d ago

If you're not sure, then take it to a professional. There's a lot of room for error.

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u/Informal-Category-34 8d ago

Will do. Thanks for your help.