SYNC 3.4 Downgrade not working

I have a 2014 MKZ that I had a 2021 Sync 3.4 console installed in. I’m wanting to downgrade to the final sync 3.3 build. Every time I try the downgrade (using the autoinstall as to not brick my system), I leave my USB in my car, I get the notification bar at the top that says “installing update”, and I leave it for hours but nothing happens. After a bit, my USB stops flashing when it’s plugged in (not sure if this is normal). Does it usually take 3+ hours, or am I doing something wrong potentially?

SYNC Region: NA

Navigation Variant: Non Nav

Manufacturer Year: MY20

Install Type: OEM Replacement

Old SYNC Version: 3.4.20021

New SYNC Version: 3.4.20021

Do you have a error message, if so what is it?

Update Method: CyanLabs Syn3 Updater - USB

You have a NON-NAV APIM which has only 8GB of memory, so you need to make room for any type of modifications by deleting Gracenotes. Once you have that done, the process will likely work. See the tutorial…
Tutorial: Sync 3.4 NON-NAV APIM: Failure to Update to Newer Version Sync 3.4 - Ford / Guides - CyanLabs Official Community

This applies to upgrading or downgrading thru autoinstall. Only perform the Gracenotes deletion and the downgrade of the version.

Thanks for the very quick reply, i’ll give this a try tomorrow. Cheers :slight_smile:

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