Hello Folks, I've done some searches for P0638 and didn't come up with much. at least not for Diesels. the ones I've come across were Mimi Cooper S and E90 M3's that have seen this issue around 60K.
They said that P0638 is rare, it's a non wear item and that it should last the life of the car...

I have a 2011 X5 Diesel in the US. I just got the code today. Is this something to drive safely with? It's not in Limp mode or antyhing. I cleared the code with AutoEnginuity. Hasn't come back yet.
I didn't even think the Diesels had a tradition type Throttle-Body, etc?
Still learning. Thanks.
I've only test drove it for roughly 5 miles without the Check-Engine-Light coming back on. Wonder if it takes 100+ miles or what?

Thanks all.