If I have to make a guess, I'd bet it ends up being a bad MAF sensor.
I had a stubborn CEL, replaced first the oil separator, light still came back on.
Replaced throttle body, light came back on. Finally...replaced the MAF sensor, which was previously inspected and thought to be good, and that solved all the headaches. Oh...and then I had a faulty brand-new MAf sensor, and the car stalled in the middle of the highway in the fast lane! Everything just cut off and it won't start. So it was replaced under warranty, and never had that bug ever again.
The MAf sensor costs about over $300. Buy it and snap it on yourself. Then get your mechanic to reset the light for free. I have been told multiple times that the film inside the sensor is super sensitive. A lot of people try to clean it, but I have been advised to just dust it clean with an air hose and not to even touch it!
Don't feel too bad. I'm sure every 5series owner has replaced the radiator and the MAF sensor before.
Together with many other common faults. It will come to an end eventually, as mine did after spending lots of dollars. I totally enjoyed it after that, it was money well spent, if I had wanted a reliable car, why...I should have bought an Accord or a Camry!
OH, btw...NOT TRUE! The 540i, especially the later models as in yours onwards are pretty reliable.
There are just the common faults that need to be fixed, as in other makes of cars.
The 540i has been the luxury sports sedan of the year for several years consecutively, until that banglelised E60 came out!
2012 Porsche 911 GTS
2008 ford F150 Foose Edition
Last edited by CosmosBlack; 11-03-2006 at 09:01 PM.