Bimmerfest - BMW Forums - View Single Post - Bad Knock Sensor With Significantly Improved Fuel Mileage
View Single Post
Old 10-31-2012, 04:02 PM
RPsX5d RPsX5d is offline
Officially Welcomed to the 'Fest
Location: Bay Area California
Join Date: Nov 2010
Posts: 1,045
Mein Auto: X5 Diesel xDrive35d
Originally Posted by ard View Post
Excellent post. . . . .

For me, the most likely piece of bad info is what the SA is telling you...wait for them to put it in writing and talk to the tech before you drive off, if you want the real story....

ard, you hit it right on the money . . . this was a case of comical mis-communication! Over the phone I heard the SA telling me they need to replace the "knock" sensor . . . what he actually said was "NOx" sensor! Now that makes a whole lot more sense! Agrees with the code my scanner read.

I met with the tech and he told me the codes they read (see attached) required them to replace the NOx sensors. He didn't think the SCR Mixer replacement and this sensor going bad was connected, just a coincidence - at least that was his best guess.

He has no idea why my fuel mileage improved by nearly 20% (from ~22.5% to over 27 mpg!). On my way back from the Dealer my mpg was about 24+ mpg (mostly hwy) . . . still higher than what I saw after the initial EGR valve replacement and associated re-programming. I will keep an eye on the mpg for the next several weeks and see where it finally settles. Since mpg is moving in the positive direction I am not complaining!
Attached Thumbnails
Click image for larger version

Name:	BMW X5 Service Report 31OCT2012 NOx Sensor Replacement.jpg
Views:	2615
Size:	189.6 KB
ID:	347975  

Last edited by RPsX5d; 10-31-2012 at 04:04 PM.
Reply With Quote