No, you can update maps without updating SYNC. I updated maps to NA 1.18 and then Sync to 19205 without issues.

 

You can also do the update with ignition ON only; no need to start the engine. I just did both the Sync and map update that way. But I hooked my Optimate6 charger before starting, to avoid running the battery down. It didn't take long to show fully charged after finishing. Better than idling the stupid engine that long, but to each his own.

 

ok. I read you needed 3.0 or map update would not install. Also was told you need 8 gig thumb drive. I did it with a 2 gig.