So..2005 S60 2.4..the fuel level sensor...the float...is built in to the fuel pump. You have to figure out if you have a plastic gas tank or a steel one. You'll also have to find which chassis number you have... which usually means.. early 2005 or later 2005. The VIN number on the dashboard has all ...

I don't know about the specific configuration on your car but you can see here after about 5:00 there are two covers under the rear seats - one is hidden under the upper section of the seat and difficult to access (need to remove the upper seat). The picture in your first post seems to be just a hol...

Is it possible the sender assy is secured to the pump unit itself ? That's how it was on my model year (and a bit tricky to remove, had to separate them inside the tank)