at least on my 530.

Quote Originally Posted by shogun
When the air-mass sensor is working normal, the hot wire does not glow. To burn off any deposits and dirt, the control system will heat the wire red hot to 1000 degrees Celsius (1800 F) for about 1 second, after you shut off your engine. This is the cleaning process and only performed if the engine is revved up to at least 2000 rpm. So starting your engine, let it idle for a certain time and shut off means no hot wire cleaning.

http://shrubbery.student.utwente.nl/...leshooting.htm