Shares of Ford Motor Co. fell 0.5% in premarket trade Tuesday, after the automaker was downgraded at Piper Jaffray, which cited concerns over Ford's ability to find compelling revenue drivers to offset secular threats. Analyst Alexander Potter cut his rating to neutral from overweight, and his stock price target to $12 from $14. Potter said he appreciates Ford's focus on "fitness," and its newfound willingness to cut less profitable platforms, which refers to the company's announcement last month to stop making sedans. "But with U.S. vehicle sales slowly eroding, we think investors are looking for more fundamental changes from Ford--and from automotive companies in general," Potter wrote in a note to clients. "Ford may yet capture its share of the $1+ trillion market for autonomous rides, but in our view, the company isn't a leader in this market, at least not yet." The stock has gained 3.9% over the past three months through Monday, while rival General Motors Co. shares have dropped 12.5% and the S&P 500 has lost less than 0.1%.