I added car registration to form near the end. How do I check if it is on my return?

You posted your question from the Free Edition.   The Free Edition does not support entering itemized deductions like car registration.  Entering such things will trigger an upgrade to a paid version.   Itemized deductions have no effect on your refund or tax due unless you have enough itemized deductions like mortgage interest or property tax, etc. to exceed your standard deduction.