Early in 2010, the National Highway Traffic Safety Administration gave up trying to force Honda to recall defective liftgates on its 2005 minivans. That hasn’t prevented the agency from opening a new investigation into a similar problem on 20,000 Odysseys from the 2009 model year.

After receiving seven complaints, the agency began investigating struts failing on the power liftgate on the 2009 Odyssey Touring and EX-L models. Two owners reported injuries from being struck, according to a document posted this week on the agency’s Web site, according to The New York Times.

N.H.T.S.A. previously investigated a similar problem on the 2005 Odyssey. In that case, the agency told the automaker in 2009 that it wanted a recall of almost 22,000 minivans because “the consequence of the strut failures — unexpected dropping and power-closing of the liftgate — poses an unreasonable risk of injury.”

In a rare example of automaker defiance, Honda refused, writing in a letter to the agency that it “respectfully declines the staff’s request for a safety recall of these vehicles.” Honda said the problem was nothing more than an inconvenience for owners.

The automaker’s position left the agency with two choices: Take Honda to court or back off. It chose the latter course in 2010, allowing Honda to inform owners of a problem and “provide the opportunity for vehicle owners to obtain new struts that are more robust.” At the time, Chris Naughton, a Honda spokesman, said the automaker considered the action a “product update.”