Had similar codes. Ended up being my MAF.

A bad MAF can throw a lean code, but the majority of the time, it is the rubber intake boot that connects the ICV and the throttle body. A genuine OE MAF is around 300-400 bucks while a new rubber intake booth is around 15-25 bucks. A vacuum leak is also a reason for a lean code.

Found it!!! Cracked rubber elbow hose (part # 13541440102)

Temporarily patched it up with sealant tape for now and observing if that's really the culprit, but looks good so far...

Are OEM replacement hoses equal in quality to original BMW hoses? Are there better replacement hoses out there?

Mishimoto make silicone boots for the M54 but I am not sure if it will work for the X5. They make them for E46 330i's.

I never looked too deeply into it since I found out after I put in an OE hose. Maybe you can email them to check?

Oooo... thanks! Sent them an email.

Cool! It would be cool if those work. The E53 X5 is the orphan child of the BMW aftermarket lol.

For $105 for a Mishimoto boot, I'll buy a Genuine BMW boot any time.

$105??? Ya... my E53 is bone stock... I don't think that's gonna help it much.

SERVICE ENGINE SOON and the engine pictogram are interchangeable, kinda. The pictogram is used on Canadian cars, SES is for the USA.

Set the key to Position II (RUN), before engine start, if you have a USA car then you will get the SES light, if the Canadian version then you get the pictogram. If you have neither, then you have trouble.