Vehicle Depreciation

I have a vehicle that was put into use in 2018.  The full cost was taken as a "Special Depreciation Allowance" that same year.  There should be no current depreciation.  BUT, when I try to enter this information into TurboTax Business it will no calculate correctly.  It keeps coming up with Section 179 for the entire cost, plus a special depreciation of an additional amount, resulting in accumulation depreciation of more than the truck was purchased for.  I put no amounts in the the section 179 box or the special depreciation allowance box.   I cannot figure this one out.