Editor's note: An earlier version of this story incorrectly characterized the failure experienced by some cylinder heads in 2011-13 model year 3.6-liter Pentastar engines. The failure is caused by excessive wear.
DETROIT -- Chrysler Group will extend the warranty for consumers who bought certain 2011-13 vehicles with 3.6-liter V-6 Pentastar engines.
The left cylinder heads of a small percentage of the engines have failed after excessive wear.
The company will extend its engine warranty on the left side cylinder head to 10 years or 150,000 miles. The remaining engine components will continue to be covered by the automaker's 5-year/100,000-mile powertrain warranty.
In 2012, about the time Chrysler was instituting its design change, executives said that roughly 7,500 engines were susceptible to the cylinder head failure. A spokeswoman for the company last week declined to say whether that estimate is still valid.
Chrysler discovered the problem in 2012 after customers began complaining that their new vehicles were exhibiting a "ticking sound" or other issues, and a check engine light illuminated.
Doug Betts, head of quality for Chrysler, told Automotive News in 2012 that the problem had been found in about half of 1 percent of vehicles with the Pentastar engine. Chrysler would not say whether the percentage of affected engines had since changed.
The 3.6-liter V-6 Pentastar is the automaker's main V-6, and is standard in several of its top-selling models, including the Jeep Wrangler and Grand Cherokee.
The company's investigation continued for months, and traced the problem to an unusual combination of factors including low-quality fuel and certain driving conditions.
"A small percentage of these 2011-2013 model year engines may be susceptible to an engine misfire which is caused by a combination of rarely occurring factors, including drive cycle and fuel quality," Chrysler wrote in a statement last week announcing the extended warranty. "The issue does not disable the engine. Dealers will replace the left cylinder head with a new part with a minor design modification."
Chrysler said it made the design modification in August 2012 and a spokesman said the company has not had any reports of the problem occurring in engines manufactured after that time.