Downgrade t420 bios

Good morning guys, i have a t420 with i7 2640m 16gb of ram, an ssd and an nvidia card, my problem is that i am on bios 1.48 and for it to work correctly i need to downgrade to 1.46, the lenovo site tells that i cant go back from 1.48, but i think it is possible, is it possible? have any of you tried it?

Thanks for all the help.

 

Yes you can change the BIOS to an older version on the T420, I 've personally upgraded and downgraded my T420 BIOS many times without issues. Be sure it has a working battery and is plugged in the mains before proceeding.

 

Thank you for replying, but can i really go back to 1.46 from 1.48 even if the lenovo site tells me it is not possible? If so i will try it. I need the dvd reader, a cd, and born the iso to the cd right?

 

I've never dealt with this, but I'll try to steer you in the right direction.

The Windows version of the bios updater doesn't need a boot disk. Try it and see if it works.

If not, trying Googling something like "update thinkpad bios error" or something similar. I know the whitelist (add-on card restriction) removal bioses often run the updater from the command line with "/s".

Something probably gets you past the "you aren't allowed to update the bios" message, it's just a matter of searching for it and trying things.

 

When downgrading using the Lenovo BIOS utility (Windows) it will warn you that you are about to flash a BIOS that is older than the one currently on the system. You can still choose to proceed however and it will downgrade the BIOS and Embedded Controller as normal.

You will also get the same warning when using the Bootable CD method but again you can still override and proceed with the BIOS downgrade.

I went from 1.46 -> 1.37 -> 1.46 on my T420 without issues, I did it mainly to try out some funky custom BIOS logos on my system!

 

Previous versions could be downgraded. But, according to lenovo, they dissabled the possibility to downgrade with the latest 1.48 version.

 

Thanks for all the responses guys, so it is impossible to downgrade from 1.48 to 1.46, i thought that it was possible to do under linux using el torito script, but i fear bricking it. Or should i try?

 

I have tried to downgrade using boot CD. It says "Error The system program file is not correct for this system."

 

Yeah I noticed the 1.48 says it can't be downgraded. I've went between older bios versions many times, I was going to try 1.48 out until I saw that notice and decided not to risk it.