Samsung Galaxy S III
GSM Radio

The Samsung Galaxy S III (SCH-I535 / d2vzw) is capable of communicating with the GSM cellular service. On a recent trip to Europe, where all carriers use GSM and none use CDMA, I planned on using my pocket computer, but it failed to connect to any carrier.

At that time I had the I535 VRLHE radio (modem) firmware installed. In Spring 2012 the phone was known to not work with GSM, but an OTA update was promised during Summer 2012 to activate it. Since VRLHE came out around September 2012, I assumed it had the patch. My assumption may or may not have been correct, but recently in September 2013 I upgraded the radio firmware to the latest version, I535 VRBMF1. Nonetheless this did not bring GSM to life.

It turns out that I already have a guide: Set up Verizon Galaxy S3 as World GSM Phone (confirmed working). By lair12, 2012-09-04. (See his forward reference to a simplification for the procedure.) If you're going to use a foreign SIM abroad, here's one procedure to get it out of Verizon LTE mode and using your foreign carrier. However, forum posters indicate that there is a simpler way.

Kosta25 (2012-11-06) posts a procedure very similar to lair12's. Among the comments, Zaid Zerox (2013-03-18) suggests a much simpler procedure, and the same method is recommended in a variety of forum posts. Here it is:

Using the normal Phone app's dialpad, I dialled *#*#4636#*#*; the numbers spell out INFO. A screen immediately opens (most likely the Phone app is responsible) titled Testing, with four categories:

• Phone Information
• Battery Information -- The usual battery stuff; most of it is available in Settings - Battery, and the rest from Phone Tester.
• Usage Statistics -- Gives how long each app has executed (since when?)
• WiFi Info -- Detailed information about each configured WiFi network; in my case the currently connected one was at the end and had extra information.

Comments refer to this magic number being used on a variety of phones, not just SCH-I535 (Verizon Galaxy S III), and on stock images, not just on CyanogenMod. However, I have not actually seen it work on other than my own pocket computer.

Procedure to use it:

• Click on Phone Information. It opens up with various useful and/or mysterious information.

• Hit the … (menu) icon.

• In the menu several items look interesting, but for this, click on Select Radio Band.

• A sub-box opens titled Set GSM/UMTS Band with apparently three choices:

  • USA Band (GSM-850/PCS-1900/WCDMA-850/WCDMA-PCS-1900)
  • Cellular (800-MHz)
  • PCS (1900-MHz)

• I clicked on the first one, USA Band. It says Set USA Band… successful.

• Use the Back button to get out of all the numerous nested dialogs.

• Now in Settings - Wireless & Networks (more) - Mobile Networks - Network Mode, you get a listbox with these choices, where before you only had the middle two mentioning plain CDMA.

  • LTE/CDMA/EvDo/GSM/WCDMA
  • LTE/GSM/WCDMA
  • LTE/CDMA/EvDo (currently selected)
  • CDMA/EvDo auto
  • GSM/WCDMA auto
  • GSM/WCDMA preferred

• I selected the first one, LTE/CDMA/EvDo/GSM/WCDMA.

• My phone reports a normal signal strength, but my cell network indicator reports No Service or Searching for Service, and this is no lie, voice and data are inoperative.

I believe this test has been successful, and I would get service in Europe, or places with GSM provided by other than Verizon's hated rivals, AT&T and T-Mobile USA. It is reported (sorry, I lost the reference) that Verizon's preferred roaming list (PRL) has negative entries specifically forbidding connecting to these carriers.

Now it is necessary to revert the band selection. But to which one? First, in Mobile Networks I reverted to network mode LTE/CDMA/EvDo. I also tried CDMA/EvDo Auto, but it immediately switched by itself to LTE/CDMA/EvDo. Then I used the *#*#4636#*#* method to select the GSM/UMTS band, with these outcomes:

So after a very nervous evening I survived this test of the GSM radio. Now the punchline will be revealed the next time I am outside the USA: can I actually use the phone with a foreign GSM carrier? According to the coverage map for Rogers (Canada), if I correctlty interpret the color codes which don't exactly match what's on the map, they offer GSM/LTE throughout Vancouver and Victoria. These are places that I'm likely to visit in the near future.