Diag codes?

[TimeTraveler7]

I've seen at an Apple service that they entered some diag codes into Safari to get more detailed info on the battery. I think the URL was like diag:####, where #### was a number. It launched an app of a sort, which disappeared after going out of foreground. Does anyone know where those codes could be obtained (Google didn't find much)?

 

[J. A.]

You enter diags:// into the Safari search bar. This is what you get next:

You need a ticket number, which you can get at the genius bar.

In this case it would be easier to go to the next Apple Retail Store and let someone take a look at your device.