The National Highway Traffic Safety Administration has officially closed an investigation into approximately 1,593,452 Ford vehicles after reviewing over 10,000 consumer complaints regarding reduction of engine power while the vehicles are moving.

The probe affected vehicles like 2009-'13 Ford Escape, the 2009-'13 Mercury Mariner, Ford Fusion and Mercury Milan with 2.5-liter or 3.0-liter engines.

The vehicles won't be recalled, according to the NHTSA.

Instead of a recall, Ford will extend warranty coverage and update the software in the affected models.

Dealers have been told to "update the powertrain calibration to improve vehicle performance in the event that intermittent electrical connectivity of the throttle body motor contacts occurs," the NHTSA said in its summary.

All vehicles are eligible for the program through next January, according to NHTSA.

"Owners of the affected vehicles will be contacted by mail to take their vehicle to a Ford dealer who will reprogram the powertrain control module to the latest calibration," said NHTSA.

An investigation was opened in February 2013 after the NHTSA received a number of complaints that electronic throttle body failure may cause a sudden reduction of engine power while the vehicle is moving.

Ford received 10,999 complaints and the NHTSA received 1,147 complaints, equaling a total of 11,960 complaints.

One injury has been listed in the NHTSA report.

"During this investigation, Ford identified a condition in subject vehicles equipped with 2.5-liter and 3.0-liter engines that may result in a sudden reduction of engine power," said NHTSA. "According to Ford, the (electronic throttle body) internal motor contacts may develop a high resistance material buildup condition on the commutator, resulting in intermittent electrical connectivity and reduced engine power."

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