Try entering into GSM test mode by dialing this
If engineering mode is enabled, it will bring up the GSM test mode.
If it does nothing you will need to modify this key in the registry.
BuildInEngineeringModeApp = 1 (to enable it if disabled)
LaunchEngineerModeAppDialStr = *#*#364#*#* (may be different for you, use whatever is listed for your device)
Just keep in mind that the device should be immobile when this is done so as to get an accurate reading.