For many years there have been ‘secret’ codes available that you could enter to perform systems maintenance tasks and gain information about the particular device. There are some codes available for the Samsung Galaxy S3, and while they don’t do a huge amount, they’re quite fun to try.
The first thing you need to do is open up the dialer app, as this is where the code is entered. The first one to try is simply ‘* #1234#’ . This will display information about the version of the phone.
Software & hardware
Next you can enter in *#12580*369# to display information about the software version your S3 is running. You’ll also see some information about the hardware that it has got inside it. To exit this, simply press the home button.
Finally, and probably the most useful is ‘*#0228#’, which will display information on the current state of the battery. This code will show you the current voltage, temperature and overall charge level. This can be used to diagnose a faulty battery.