JPMorgan Chase & Co., the lender that lost almost $2 billion during Chrysler Group LLC’s 2009 bankruptcy, is now its chief adviser as the automaker’s two owners haggle over its value, Bloomberg News reported yesterday. JPMorgan will advise Chrysler in the event of its sale to majority shareholder, Fiat SpA. The bank was also listed this week as the lead underwriter of an initial public offering of Chrysler shares owned by the company’s other shareholder, a United Auto Workers retiree trust. The dual role highlights the complicated path Chrysler has been forced to take to resolve a dispute between its two backers. Sergio Marchionne, the chief executive officer of both Chrysler and Fiat who has spent four years seeking to merge the companies, is at loggerheads with the UAW’s trust over the value of its 41.5 percent stake in Chrysler. Letting public investors put a price on the stake, through the IPO process, is one way to resolve the matter.