"These results are consistent with what we've seen in recent years," said Mike Battaglia, senior director of auto retail at J.D. Power. "They've been underperforming in customer service at dealerships relative to the rest of the industry."
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The J.D. Power study is based on the responses of 70,000 owners and lessees of 2010 to 2014 model-year vehicles.
Fiat Chrysler did not immediately respond to a request for comment.
Since coming out of bankruptcy in 2009 under the ownership of Fiat, sales for the Chrysler, Dodge, Jeep and Ram brands have rebounded. Thanks to a slew of new models and fresh marketing, Fiat Chrysler's U.S. market share has climbed from 8.9 percent at the end of 2009, to 12.7 percent at the end of last year.