This is an original research, please mention me or this post if you forward this post to any other medium. Before you start to do anything, please read the following descriptions, they are very important.

1. This article is for research only, enable ECG feature might be illegal in your region and country. 
2. Apple could change the rules in any time without any notification.
3. This method is not like iCloud data merge method, if you try to pair Apple Watch to another iPhone with your iCloud account, you may need to do this tutorial again. 

Requirement：

1. Apple Watch S4 or above (of course)
2. Any iPhone which can pair that Apple Watch
3. iOS and watchOS combination in the following table. I don't know whether this will be blocked in the future, so do it as soon as possible!
4. iMazing App. It's available for both PC/Mac. But your operation system must be 64bit if you use PC.
5. ECG activation file (v1, v2) , extract it and get a .plist file.
6. You should open "Health" app on your iPhone at least once.

 

iOS and watchOS combinations：

iOS	watchOS	Can use this hack to activate
12.2 ~ 13.1.1	5.2 ~ 6.0	Unknown, maybe works
13.1.2 ~ 13.3.1	6.0.1 ~ 6.1.3	Yes, but requires EER
13.4 ~ 13.4.1	6.2 ~ 6.2.1	No
13.5 ~ 13.7	6.2.5 ~ 6.2.8	Yes, any region
14.0 ~	6.2.5 ~ 6.2.8	Yes, any region
14.0 ~	7.0 ~ 7.0.1	No
14.0 ~ 14.2	7.0.2 ~ 7.2	Yes, any region
14.3	7.2	See below

Warning: It's very possible that your device would get Apple logo boot loop after you restoring your backup on iOS 14. This is bug on iOS 14 which is not caused by iMazing. You may need to restore both your iOS firmware and backup multiple times if it failed.

PS: If you used iCloud method, or your country/region supports ECG v1 but not v2, then you can use v2 plist to upgrade your ECG version. However, if you used iMazing method or jailbreak method (ECG Enabler), or you never have ECG function before, please don't update to iOS 14.3 and watchOS 7.2 because they blocked this method. Maybe it's a bug like watchOS 7.0 ~ 7.0.1 and will be fixed later.

 

Testing Environment：

1. iPhone XR iOS 13.1.2 Taiwan model
2. Apple Watch Series 4 watchOS 6.0.1 Hong Kong model
3. Japan iCloud account (Doesn't matter)

 

From the previous research with x43x61x69, we noticed that the iPhone with Apple Watch which enabled ECG, would write two "flags" to Health database. In terms of theory, we can write these two flags by ourself, then enable ECG directly. However, after more researches, I found that there's an easier way to do this without modifying database. Anyway, you should modify the backup file of your iPhone, so get iMazing app if you don't have, it's the best choice to edit iPhone backups.

 

First, please unpair your Apple Watch, then use iMazing to make an encrypted backup. Please enable "Backup Encryption" from "Options".

▼ You must enable Backup Encryption or the health database won't be backed up.

 

▼ After applying the options, click Backup to make a backup immediately.

 

▼ Then, click the button above, choose the backup file we just made, and then choose "Edit".

 

iMazing would ask you to make a "backup of your backup", confirm that.

▼ Now you can find "Editable Backups", choose the one we made, choose "File System" and go to the directory of HomeDomain/Library/Preferences

 

Unarchive the ECG activation file, you would get a file named com.apple.private.health.heart-rhythm.plist

▼ Click "Copy to Backup", make sure it's under HomeDomain/Library/Preferences directory.

 

▼ Choose the backup file we modified, click "Restore to Device", follow the instructions.

 

▼ Do not check "Erase target devices" if you have eSIM installed, it may erase your eSIM too. If your storage is not enough for restoring a backup, try to delete some photos (because you will recover them after restoring), or do a DFU restoring to clean all contents. (DFU restoring doesn't remove your eSIM)

After restoring your iPhone, now you can pair your Apple Watch. Please don't restore Apple Watch backup file.

Now you can use ECG on your Apple Watch. If your ECG app on your Apple Watch get stuck in "installing", try to reboot your Apple Watch and see whether it would be solved. If not, you should unpair and pair again.

 

Special thanks: x43x61x69, @HuangIYang, Garynil and Francis, this research can't be done without their help.