Sales in 2019 are averaging 16.9 million (average of seasonally adjusted rate), down 1.5% compared to the same period in 2018.
This graph shows light vehicle sales since 2006 from the BEA (blue) and an estimate for July (red).
A small decline in sales to date this year isn't a concern - I think sales will move mostly sideways at near record levels.
This means the economic boost from increasing auto sales is over (from the bottom in 2009, auto sales boosted growth every year through 2016).
Note: dashed line is current estimated sales rate of 16.82 million SAAR.