See the first link below in my signature.

Vacuum leaks, vacuum leaks, vacuum leaks.

Intake elbow, CCV lower oil return hose, CCV hoses, SAP hose, valve cover gasket, DISA O-ring.

 

Took it to my mechanic this morning. His scanner only showed the 074 system running lean. He unplugged and cleaned out the maf and did a reset. All warning lights are gone for now I also had the transmission warning light prior to the check engine light, that's gone too. My fingers crossed right now, gotta play the waiting game ....

 

Your codes are not complete. There are ALWAYS 5 digits, the first is an alpha character (usually P, which denotes a Powertrain issue), followed by 4 numerals that usually have a zero or a one for the first character. If zero, then the code is a generic engine management code that means the same thing on all cars or trucks that can generate that code -- P0301 _always_ means MISFIRE, CYLINDER #1 -- and if one then the code is unique to BMW -- other makes can produce the same code, but the meaning might not be the same as assigned by BMW

You have P0171 and P0174, which mean LEAN, BANK 1 & LEAN, BANK 2. Lean is most often a vacuum leak where air is entering the system after the MAF. All air is supposed to pass through the MAF, but if you have a leak after the MAF, then air gets in that the MAF has not seen, and this causes the fuel mixture to be lean. There can be other problems, but a leak in the intake track is by far the #1 source of LEAN codes.

 

P0171 P0174 that's the codes they gave me at autozone, when my mechanic used his scanner only the P0174 was showing. I'm gonna replace the intake boots first then if the problem still there ill buy the new maf....

 

Why? The MAF is non-refundable and runs to about $300. You really want to be sure you need one.

You can cover your ears and stomp around in the field looking for the land mine if that's how you want to find them -- I call this the Polish Mine Sweeper method (apologies to the Polish mine sweepers out there).

The diagnostic port will tell you if the MAF is working, or not.

 

Not likely the MAF unless you are triggering lean codes at 40+ MPH.

Your MAF should be reading about 5 grams/sec at idle as I recall, however, this can vary due to other things as well.

Not likely your intake boots if the codes were cleared, then did not come back quickly. That being said, if you have original intake boots, they will need to be replaced soon anyway.

You really need to inspect the CCV hoses and the CCV lower oil return line, this is a very common failure that is usually hard to find.

Again, read the first 2 links below in my signature at least 2 times and you will know what the most the common problems are.