I bought my Lumia 920 yesterday and wanted to have that diagnostics tool I knew from my Lumia 800 / Windows Phone 7.
On my Lumia 800 I just had to enter ##634# into the phone keyboard and then that tool launched and was available in my app list.
Now I tried to get this tool back (e.g. to see the current detailed battery status) but the above code only opened a "Color Variant + Life Time Counter" tool which is quite useless.
Is there a possibility to get this or a similar tool on my Lumia 920?