How To Guide OnePlus 9 Pro: How to switch between Color OS and Oxygen OS without unlocking the bootloader

[Fatal_Scythe]

Here is a lengthy way to get this working on a EU 9 Pro with WORKING SIM card. I just completed my first phone call! Only do this if you know what you are doing and if you are familiar with the concepts of flashing ROMs, using fastboot to flash partitions and possibly using the MSM tool to restore your device in case something goes wrong. I told you.

Steps to switch from OOS>COS on non-chinese OnePlus 9 Pro. Credits to: Telegram user SamuraiTronVC

Note: This whole process will wipe your data.


1. Install Android A12 Beta 1 by OnePlus via Local Upgrade.


2. Once booted into A12 Beta, install the custom Local Update APK that they provide.


3. Install the ColorOS Dowgrade package and reboot.

__________

Here is how to fix the missing network on 9 Pro. I tested it with my own LE2123 EU 9 Pro, but since the A12 DP is working on IN and NA versions as well, should work for everyone. I updated to the latest ColorOS build after step 3, A.08. Don't know if that is required, but do it anyways. The phone has been behaving a bit weird after doing this - e.g. boot loops once, but then it works etc. Not sure if it has to do with steps 4-6, but proceed with caution. Credits to: Myself.

__________

4. Extract the modem.img from the A12 DP using Payload Dumper. I did it already and you can download it here, but feel free to extract the .img yourself.

5. Unlock your bootloader: fastboot oem unlock

6. Flash the modem.img: fastboot flash modem modem.img

Hi, I'm kinda stuck at the 1. Step already, System-Update just says "Update Installation failed." when trying to install the A12 Beta.

Is there any specific OOS Version I have to be on? I tried on 11.2.8.8 and 11.2.9.9 but both times it fails with the error above.

Thanks in advance. ^^

 

[peking_man]

Planning to buy a OnePlus 9Pro here in China - apologies for what is probably a dumb question, but to convert from ColorOS to OxygenOS is it still necessary use the downgrade ROM process? Or if there is a newer Oxygen version compared to the one the phone comes with, can I just use a direct local upgrade process?

I understand that when the OnePlus 9/Pro was first released the downgrade route was necessary, just not sure if that is stlll the case. I last did this 4 years ago with a OnePLus5 - and it seems some things have changed since then ...!

 

[brmbjn]

I am on oxygen c.39
Can i flash color c.39 ? Without data lose ?

 

[prembhullar]

Can anyone please help VoLTE don't work for me..when I first bought this device model was le2125 and I went to color is and now even model has been changed and VoLTE don't work.

 

[Annki81]

Friends, I need help by !

I have an OP9 Pro (V.CN / global rom / ColorOS V11.2 / Android 11), which package should I download to use Portuguese apps and language in Brazil?

Downgrade packages:
Color OS for OnePlus 9 Pro
Oxygen OS for OnePlus 9 Pro

 

[Creazybull]

Tried to do the same way as instructed but still facing verification fail problem. Device is Chinese version of OnePlus 9 Pro with color os!

 

[elchmartin]

Planning to buy a OnePlus 9Pro here in China - apologies for what is probably a dumb question, but to convert from ColorOS to OxygenOS is it still necessary use the downgrade ROM process? Or if there is a newer Oxygen version compared to the one the phone comes with, can I just use a direct local upgrade process?

I understand that when the OnePlus 9/Pro was first released the downgrade route was necessary, just not sure if that is stlll the case. I last did this 4 years ago with a OnePLus5 - and it seems some things have changed since then ...!

Very interested in the answer to this, too.
Getting my 9pro in 2 days (if everything goes well).

But I am also willing to try anyway.... Will keep you posted ;-)

 

[elchmartin]

small update:

my device came, CN-version, but already flashed EU-ROM by the dealer. So I did not do a thing, it updated to tha latest version itself.

 

[Annki81]

small update:

my device came, CN-version, but already flashed EU-ROM by the dealer. So I did not do a thing, it updated to tha latest version itself.

but, was the flashed EU-ROM ColorOS or OxygenOS?

 

[elchmartin]

but, was the flashed EU-ROM ColorOS or OxygenOS?

it stated to be OxygenOS.... Still is...

 

[Annki81]

it stated to be OxygenOS.... Still is...

Oh man, I downloaded all possible versions and I can't load locally. "Verification failed" always appears

OP 9 Pro / V.CN LE2120/ ColorOS 11.2 currently.

 

[Annki81]

Cara, baixei todas as versões possíveis e não consigo carregar localmente. "Falha na verificação" sempre aparece

OP 9 Pro / V.CN LE2120 / ColorOS 11.2 atualmente.

 

[Juan_le_Elevated]

I'm currently on Coloros12 LE2120
Does the downgrade package work for coloros 12 to oxygenos 11?

 

[winnertt]

I'm currently on Coloros12 LE2120
Does the downgrade package work for coloros 12 to oxygenos 11?

Same question here

 

[lgv20v30]

here is my test result .

1. update to the Android 12 then roll back to color os.
2.flash the provided link for Modem ..work ok with4G but no 5G im in the US with the USA model so maybe i need to flash my own modem to work ...
3. Flash the tmobile Modem found on XDA and messup my phone bricked it !! but msm save me .


after flashing the Tmo modem im keep getting Qualcomm dump Crush screen, ....


i get that screen when I first time flashes schwarzerfleck's modem . but after reboot it is fine...

also what I notice is every OTA update will kill the modem u will need to reflash the modem to get
data/call working ...


if anyone would like to chat about this please pm ur telegram we can share our experience.

When you flash modem, were you on Color OS 11 A.8 (as in the original post), 11 A.13 (current incremental update will go straight to A.13) or 12 C.44 ? Thanks. I tried all 3 and all got Qualcomm dump screen on Le2125.

 

[thepublocal]

Flashed full ColorOS A12 (NOT OOS12) onto my OP9pro last night and have to say I am amazed on how smooth the experience is. Takes about 5 mins to debloat the chinese bloat off of it and its all good.

I am amazed how there aren't other people flashing this on to the device !

 

[lgv20v30]

Flashed full ColorOS A12 (NOT OOS12) onto my OP9pro last night and have to say I am amazed on how smooth the experience is. Takes about 5 mins to debloat the chinese bloat off of it and its all good.

I am amazed how there aren't other people flashing this on to the device !

Great to hear that. Which variant of OP9pro (EU, IN, NA) you are using ? Which version of A12 (C.44, etc) ? Do you need to flash modem or get root to have network working ?

 

[thepublocal]

Great to hear that. Which variant of OP9pro (EU, IN, NA) you are using ? Which version of A12 (C.44, etc) ? Do you need to flash modem or get root to have network working ?

EU model (non root) and I haven't actually put a sim in it yet to test network but have read patching modem is simple enough?

 

[lgv20v30]

EU model (non root) and I haven't actually put a sim in it yet to test network but have read patching modem is simple enough?

In my case after flash modem and start using data of sim card, it either boots loop or shows qualcomm dump screen on Coloros C.44. Not that simple.

 

[thepublocal]

In my case after flash modem and start using data of sim card, it either boots loop or shows qualcomm dump screen on Coloros C.44. Not that simple.

ColorOS 12 LE2123_11_C.44 working data with both EE and O2 sims (UK)