Where can I find my second year vehicle depreciation expense amount? The system says it has info from my 2018 return and will calculate depreciation, but I do not see

The program has worksheets for almost everything ... save a PDF of the return with the worksheets in the Print center.  For 2018 download a current PDF which will include that form.

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See this TurboTax support FAQ for accessing prior year online tax returns - https://ttlc.intuit.com/community/prior-year-return/help/how-do-i-access-my-prior-year-return/01/270...

You might not necessarily have a second year of depreciation.  If you used Bonus Depreciation and/or Section 179 in the first year, in SOME cases you might not have depreciation the second year.