[X Play Q&A, Help & Troubleshooting] jellysheep:
Hi,

follow the steps below to enable dual-SIM functionality on a single-SIM XT1562 device.

IMPORTANT: Read the following before performing any of the steps below!

This HowTo is only for XT1562 devices. This has been reported to not work on XT1563 devices.

The second SIM in your phone will have an IMEI of "0" (as there was none set during manufacturing). In some countries like the UK, many providers don't allow phones with such an IMEI, so you will not be able to use SIM cards from these providers as your second SIM.

Only one SIM (the one used for data connection) can use 3G/LTE bands. The other SIM card can only use 2G bands (this is a hardware limitation of the device). In some countries like Sweden, some providers sell cards that can only use 3G and not 2G, so you will not be able to use these cards as "secondary" (calls/messages only) SIM.

If you plan to do a Nandroid backup or use Titanium Backup for your data currently on your phone (because you don't want to copy your data by hand) or if you want to flash a custom ROM like CyanogenMod, you will need to unlock your Moto X Play (instructions below). Note that in this case your device warranty will be void.

Here are the steps to enable dual SIM functionality:

If you want, make a backup of all your data. You can copy your files by hand, to not lose your warranty.

If you don't copy your files by hand but with Nandroid backup or Titanium Backup (to restore app data as well), you will have to unlock your device, and therefore lose warranty (Refer to this guide for unlocking: http://www.gammerson.com/2015/08/steps-how-to-unlock-bootloader-of-moto-x-play.html. Note that all your data will be lost, and your device warranty will be void.). In this case, easiest way is to boot up a custom recovery (see this thread) and make a Nandroid backup to an external SD card. Alternatively backup the apps with Titanium Backup and copy the internal SD card files by hand.

Flash a dual-SIM stock firmware: Find a stock firmware that matches your region best on this site (search for "XT1562" and "DS" for dual-SIM). Follow this guide completely for flashing the firmware on your device.

If you are fine with the stock ROM and don't need a custom ROM like CyanogenMod, and you copied your files and data by hand without root, you are now finished and can use your dual SIM phone.

If you want to flash another ROM, or restore a Nandroid backup or Titanium Backup, please continue with the following steps.

Flash your favorite ROM (e.g. @squid2's CM 12.1, it's running great), or stay with the stock ROM.

Unlock your Moto X Play (if not done for the backup before yet): Refer to this guide for unlocking: http://www.gammerson.com/2015/08/steps-how-to-unlock-bootloader-of-moto-x-play.html. Note that all your data will be lost, and your device warranty will be void.

If you're on stock ROM, flash a custom recovery (see this thread again) and root your device by flashing SuperSU from the recovery.

Restore your Nandroid or Titanium backup.

If you're not on stock ROM, add the following lines (needs root) to a new file /data/local.prop or append it at the bottom of /system/build.prop:

ro.gsm.data_retry_config=default_randomization=2000,max_retries=infinite,1000,1000,80000,125000,485000,905000
persist.radio.plmn_name_cmp=1
persist.radio.force_get_pref=1
persist.radio.multisim.config=dsds

I'd prefer the /data/local.prop, as you do not need to make the change on every ROM update.

If you're on CM 13, you will have to add this line as well:

ro.telephony.ril.config=simactivation

Make sure that either file has read/write permissions 644 and is owned by root:root (with 'chown'). To ensure the r/w 644 permissions, go into the properties of the file (e.g. with ES File Explorer), and check that the file is readable and writable (rw, or 6) by the owner, and readable (r, or 4) for the group and others.

Finally, reboot one last time.

Disclaimer: I do not take responsability for any damage that may be caused to your device or for the warranty that will be void after following this HowTo. Please make sure you have an appropriate device (XT1562) before flashing the dual-SIM stock firmware.

Credits go to [MENTION=6223408]ALD76[/MENTION] for originally posting the build.prop/local.prop modifications above, and to all the testers who risked their devices to try this out and encourage other users. And to [MENTION=6359432]heisert[/MENTION], for mentioning that unlocking is not necessary for flashing official firmwares. And to [MENTION=5293805]GtrCraft[/MENTION], for the local.prop modification line on CM 13.

Have fun and enjoy your dual-SIM phone. :D

jellysheep