Check Engine light came on with a code of P0172 http://www.obd-codes.com/p0172
I live on an island without a Volvo dealer. I'm fairly mechanically inclined and figured I'd clean the MAF sensor. Did it on my truck a couple years ago. Please help me identify it here in the attached image. I'm guessing #2, but please confirm before I open it up. I more than likely have the necessary tools. I have a few different torx sets including security torx.

 

Looks like it may actually be #1, a MAP sensor used instead of a MAF sensor? http://en.wikipedia.org/wiki/MAP_sensor

#3 is Volvo PN 8658493 which is a MAP sensor.

#1 is Volvo PN 8658471 which is a Mass Airflow Meter, but not 'sensor', are they the same?

It is said that cars which have a MAP don't also have a MAF sensor, it is one or the other.

 

This is 14 years later, but in case anyone else gets here looking for the same info (as I did), here are the answers (for a 2005 S40 2.4i):

#1 is the MAF Sensor. There are 2 T15 screws holding it in (on some models the screws are T15 security screws with the circle in the middle -- you need a special tool. I didn't have those). Once you get the screws out (be sure not to drop them into the engine bay), the MAF sensor can be slid out of the opening to be cleaned. You'll need to unlatch the electrical connector, which can be quite stuck after 10+ years.

#2 is the throttle. On the T5, it is placed in a different part of the engine, with the turbo.

#3 is the MAP. It is a working part on the 2.4i. Two T15 screws unlatch it. It doesn't appear that there is anything to clean here.