[zoso4534]

Hi, I wanted to contribute some knowledge for anyone else who runs into this problem.

Car went in for routine service at private shop and came home with a CEL. I pulled P0171, running too lean. Shop found no vacuum leaks. They changed the fuel vapor solenoid, returned the car to me, but the CEL came back. This was about a week later.

I spent a bunch of time online learning how to read fuel trims. I used my scanner to pull live STFT, LTFT, and other data points to help diagnose the issue and differentiate between a vacuum leak, MAF, and other potential problems.

Had a feeling it was the MAF sensor. I'm no stranger to German cars and MAF issues. The MAF on the G20 is so easy to remove - pop off the connector, remove two T20 screws. Nothing is in the way, so it takes just a few minutes to remove. Cleaned with MAF cleaner from auto parts store for $9.99. Put the MAF back in and no more CEL!

Word of warning: A new BOSCH-made MAF for the G20 is about $100 online. I called my local BMW dealer's parts department and they wanted $600. I didn't ask, but I bet they would have charged me $300-$400 to remove the two screws to install it.

This is why I rarely, if ever, go to dealerships.