I got an unlocked GSM Galaxy Nexus (GT-I9250) phone from Amazon a few months ago and I've been wondering why it was still sitting on Android 4.0.2 (Icecream Sandwich). Looking at "Settings | About phone | System updates" told me that my "system was currently up to date" despite the fact that most of my friends had been running 4.0.4 for a while on their Galaxy Nexus.
It turns out that a colleague of mine, who managed to buy this phone just before Apple got it banned in the US, found the reason: it was set to get over-the-air (OTA) updates from Samsung, not Google. Samsung has been sitting on this one for a while, which isn't great given the random crash+reboots that seem to occur about once a week on 4.0.2
Finding who delivers updates to your phone
Apparently there is a text file somewhere on the phone that will tell you whether it is a Google-controlled or Samsung-controlled phone. If you know what file that is, please leave a comment, I couldn't find it. So I ended up temporarily installing this application (warning: contains gratuitous ads) and looking at the "Brand" field.
Another thing you can look for is whether or not your device is running a "yakju" firmware (see the "Product" field). If it's something like "yakjujp", then you're not with Google and updates may not be available yet.
Switching to the standard Google firmware
In order to get your updates from Google, you can switch to the vanilla "yakju" firmware.
The whole procedure can be summarized like this:
- Backup your phone.
- Unlock the boot loader (which erases everything).
- Reboot into fastboot (hold down Volume Up and Volume Down then press the power button).
- Flash all of the different firmware images.
- Reboot and reinstall/reconfigure apps.
In any case, a few hours later, I ended up with a fresh install of the 4.0.4 yakju firmware and an unlocked boot loader. The only thing I haven't been able to do yet is to re-enable full disk encryption. I'm not quite sure why my phone refuses to start the encryption process...