There is once when T-Mobile rolling out Android 4.1.2 Jelly Bean update to LG Optimus L9 but was pulled back due to the instability of the firmware. After being improved and fixed by LG, the official Android 4.1.2 Jelly Bean for LG Optimus L9 is finally released to the public as stable version.
This update is codenamed P76920f and with added security enhancement as described in T-Mobile official website. Besides, it is also the cross-version update from Android 4.0.4 Ice Cream Sandwich to Android 4.1.2 Jelly Bean. The update package is 350MB in size. We highly recommend to connect your device to a stable connection during the downloading of update file.
To download OTA update from T Mobile, go to Menu-> Settings –> About device –> System Update. If you have connected to WiFi, tap on OK. It have been reminded by T-Mobile that you will receive the message The device is up to date if the maximum daily download limit is reached. Please wait for the OTA update to arrive.