Sync 4 does not support CGEA 1.2, so this will not work in your vehicle since it is CGEA 1.2. Sync 4 supports CGEA 1.3 at his time.
Likely the unit is unable to boot due to no memory available. It is possible to rescue this one using the FMods tools and jailbreak.
You need a Sync 3 screen, the video drivers are completely different from Sync 3 to 4.