Stocks struggled to stay positive at Friday's opening bell. Traders are waiting for the consumer sentiment data after a weaker-than-expected inflation report. U.S. producer prices fell 0.5% in February, economists were expecting an increase of 0.3%. Core producer prices, excluding volatile items like food and energy costs, also fell 0.5%. The Wall Street Journal says an investigation is underway involving potential stock manipulation of Herbalife (HLF). Prosecutors are interviewing people tied to investor Bill Ackman, who has had a long-standing short position in Herbalife. Late Thursday, General Motors (GM) recalled nearly 64,000 Chevrolet Volts from the 2011 to 2013 model years over carbon monoxide concerns. Two injuries have been linked to the issue.