Do I need to file section 321 shipments in ACE if I'm driving commercial shipments across the border in my car?

Do I need to file section 321 shipments in ACE if I'm driving commercial shipments across the border in my car?

Yes, you do.  As of January 1st, 2019 all low-value shipments must be manifested in ACE.  If you don't have a SCAC code you must also apply for a SCAC code from the NMFTA.  https://secure.nmfta.org/New/Introduction.aspx