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Samsung Galaxy S III
GSM Radio

Jim Carter, 2012-10-23

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:

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:

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:

Function USA Band PCS 1900MHz Cellular 800MHz
Service None Verizon Verizon
Net Type None LTE LTE
Call out No service Does not ring Connects
Call in Nothing Does not ring Connects
Cell data Nothing Connects Connects

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.