Shares of TrueCar Inc. TRUE, -1.01% tumbled 4.1% in premarket trade Thursday, putting them on track to open at a 16-month low, after the online provider of auto pricing data was downgraded at J.P. Morgan, which cited weak auto industry trends and execution risk. Analyst Doug Anmuth cut his rating to underweight from neutral, and slashed his stock price target to $10 from $13. He said he's concerned that industry light vehicle sales have declined 1% year to date, and that dealers are turning cautious, as evidenced by dealership operator Group 1 Automotive Inc. GPI, +1.12% warning earlier this week about weak market conditions and pressure on used-car margins. Anmuth said TrueCar's investment in the Capsella project is a positive, he believes the investments will take time to "move the needle" on earnings. "In addition, we are cautious around emerging headwinds in the auto industry that could weigh on near-term performance," Anmuth wrote in a note to clients. The stock had plunged 12.0% over the past 12 months through Wednesday, while the S&P 500 SPX, -1.64% has gained 1.1%.