The National Highway Traffic Safety Administration investigated Ford Fusion and Mercury Milan sedans and Ford Escape and Mercury Mariner crossovers from model years 2009 to 2013 after receiving reports of possible fuel system problems that could cause a sudden loss of engine power.

NHTSA received about 12,000 complaints on the issue, most of them first reported to Ford. There was one report of an injury but no crashes or deaths related to the issue, NHTSA records show.

The agency said closing the investigation did not constitute a finding that a safety-related defect does not exist.

During the investigation, Ford and its suppliers updated the powertrain control module software, developed a remedy and announced a "special customer satisfaction program," that extends the electronic throttle body warranty to up to 10 years or 150,000 miles.

The electronic throttle body is part of the engine's fuel delivery system.

Customers will be notified by their Ford dealers, who will reprogram the powertrain control module.

(Thsis tory fixes typo in first paragraph.)

(Reporting by Bernie Woodall in Detroit; Editing by Jonathan Oatis)