Last fall, we told you about, an iPhone code that helps diagnose problems connecting to AT&T's 3G network. Dialing *3001#123456#* and pressing "Call" starts a field test on your iPhone with results that can be used, for example, to gauge signal strength. (It also offers a slew of other information probably beyond your comprehension unless you happen to be a cellular engineer.)
While the above code above is the iPhone's most useful, there are a number of other interesting codes, many posted at methodshop.com. According to the site:
Most cellphones use special "diagnostic codes"--numbers that can be dialed to display various technical information about the unit, the user's account, the cellular network it's "registered" on, or the local network that's currently available. You might have dialed a few of these already while on the phone with tech support. ... Some of these may work your non-iPhone phone. Some are AT&T- or North-America-specific. The only way to know if they work on your phone is to try.
We tried each of the below codes and included sample screenshots of the results:
Dial *#06# if you need to know your iPhone's IMEI, the unique identifier (i.e. serial number) for your cell phone hardware. The IMEI, along with your SIM, identifies your iPhone to your service provider.
Dial *777# and press Call checks your prepaid account balance.
Dial *225# and press Call checks your bill balance for a postpaid iPhone.
Dial *646# and press call checks your minutes for a postpaid iPhone.
Dial *#21# and press Call shows the status of call forwarding for voice, data, fax, sms, sync, async, packet access, and pad access call forwarding enabled or disabled.
Dial *#30# and press Call shows whether you have enabled or disabled the presentation of the calling line, presumably the number of the party placing the call.
Dial *#76# and tap Call shows whether the connected line presentation is enabled or disabled.
Dial *#43# and tap Call and show the call waiting status for voice, data, fax, sms, sync data, async data, packet access and pad access. Each item is either enabled or disabled.
Dial *#61# and tap Call to show the number for voice call forwarding when a call is unanswered. Also show the options for data, fax, sms, sync, async, packet access and pad access.
Dial *#62# and tap Call is the same as above except for no-service rather than no-answer scenario.
Dial *#67# and tap Call checks the number for call forwarding when the iPhone is busy.
Dial *#33# and tap Call checks for call control bars by checking all the usual suspects (voice, data, fax, sms, etc) to see whether barring is enabled or disabled for outgoing.
Did you find these codes to be useful? Do you know of any other codes not listed here? Let us know in the comments below.