How to Downgrade ASUS Zenfone 4 A400CG from Lollipop 5.0 to Kitkat 4.4

Today ASUS Zenfone Blog will show you How to Downgrade ASUS Zenfone 4 A400CG From Lollipop to KitKat.

Downgrade Step (From L to KK)

1. Download the downgrade tool: UL-ASUS_T00I-WW-9.9.9.0-user.zip
2. Using MTP connecting A400L with PC. (Enable MTP: Setting-->Storage-->press the USB icon on right corner--> Enable MTP)
3. Copy the tool (V9.9.9.0) to the A400CG internal storage.
4. Remove the USB cable, the device will pops up the system upgrade information.
5. After downgraded, device will auto reboot and perform factory reset.
6. After finished, please go to Settings->About-> software information->Build number. The version should be V6.6.3

ZENFONE 4 Downgrade Version
WW VERSION

Description

ASUS ZenFone 4(A400CG) downgrade SOP (Downgrade from L to KK), V9.9.9.0 Only for WW SKU* Notice: 1. Only apply to same SKU update, Example: WW->WW, CN->CN, TW->TW. 2. Software update cannot transfer the software SKU and downgrade the software version. 3. Downgrade image will only revert back to latest KK version 4. After OTA downgrade, device will perform factory reset automatically.then reboot automatically to complete upgrade process 5. System upgrade may cause part of data missing, please buckup your important data before system upgrade

File Size	825 MBytes                                                                              2015/05/29
Download from	Global

ZENFONE 4 Downgrade Version
CHT VERSION

Description

ASUS ZenFone 4(A400CG) downgrade SOP (Downgrade from L to KK), V9.9.9.0 Only for CHT SKU* Notice: 1. Only apply to same SKU update, Example: WW->WW, CN->CN, TW->TW. 2. Software update cannot transfer the software SKU and downgrade the software version. 3. Downgrade image will only revert back to latest KK version 4. After OTA downgrade, device will perform factory reset automatically.then reboot automatically to complete upgrade process 5. System upgrade may cause part of data missing, please buckup your important data before system upgrade

File Size	866 MBytes                                                                              2015/05/26
Download from	Global

TW available Soon

Android L Release Delayed Due To Zenfone Verification Process Problem

Sad news for ASUS Zenfone 4, Zenfone 5, Zenfone 6, and Padfone S user. Today ASUS via Zentalk Super Moderator announced that ASUS will postpone Android L upgrade because verification process problem. Zenfone 1st Generation scheduled to get Android 5.0 L in Mid May, but with this announcement they will rearrange Android L upgrade schedule. This is the original post:

Android L升級延遲公告謝謝各位用戶長期以來的支持，原訂於５月中提供ZenFone4、ZenFone5、ZenFone6、PadFoneS等機型升級至Android L系統，由於團隊在驗證過程中發現了一些問題，為了避免升級之後影響相關使用經驗，因此決定將Android L延期釋出，技術人員會加緊進行問題之修復, 完成後將盡早釋出。

另外，The New Padfone Infinity (A86) 因處理器原廠不支援此款手機所採用的CPU 升級至Android L系統，因此我們將停止升級Android L之計劃；未來華碩仍會基於Android 4.4版提供此機型之軟體更新。

特此公告並請見諒。

English Translation:

Android L upgrade delay announcement

Thank you for your continued support users, originally scheduled for mid-May to provide ZenFone4, ZenFone5, ZenFone6, PadFoneS other models upgrade to Android L system, because the team found some problems in the google verification process, in order to avoid the impact of relevant experience after upgrade , it was decided to postpone the release of Android L technician to fix the problem will intensify, release as soon as possible after completion.  In addition, The New Padfone Infinity (A86) because the original processor does not support CPU used in this phone to upgrade to Android L system, we will stop the planned upgrade Android L; future Asus Android version 4.4 will continue to provide on this machine type of software update.  Notice is hereby given, and please forgive me.

Source