Visteon Warns on Earnings  CHICAGO (Reuters) - Visteon Corp. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=VC.N target=/stocks/quickinfo/fullquote"&gt;VC.N&lt;/A&gt; warned on Thursday  that second half results will be well below prior forecasts as  its major customer Ford Motor Co. &lt;A HREF="http://www.investor.reuters.com/FullQuote.aspx?ticker=F.N target=/stocks/quickinfo/fullquote"&gt;F.N&lt;/A&gt; cuts production, and  steel and fuel costs climb.