Unable to scan wifi with iwslist when network-manager down

Question

I try to scan wireless networks.
If network-manager service is up and wifi interface connected, iwlist give only one cell - the same it connected with, but if I try disconnect wifi interface by shutting down network-manager interface, iwlist give no result at all.
Also if I try to start up networking service.

user@comp-nam:~$ sudo iwlist wlan0 scan | head -n 2
wlan0     Scan completed :
          Cell 01 - Address: 2E:2F:97:D7:22:24
user@comp-name:~$ sudo service network-manager stop
network-manager stop/waiting
user@comp-name:~$ sudo iwlist wlan0 scan
wlan0     Interface doesn't support scanning : Network is down

user@comp-name:~$ sudo service networking start
networking stop/waiting
user@comp-name:~$ sudo iwlist wlan0 scan
wlan0     Interface doesn't support scanning : Network is down

I use Ubuntu 12.04.1

Answer 1

Turn on the interface, not the network manager.

sudo service network-manager stop
sudo ifconfig wlan0 up
sudo iwlist wlan0 scan