Honda is going to replace the front bumpers on about 12,000 Fits it has already sold because the small car failed a key crash test.

The automaker announced the free program Thursday, at the same time the influential Insurance Institute for Highway Safety said a crash test of the 2015 Fit equipped with a redesigned bumper structure earned an “acceptable” rating on its small overlap crash test. The test simulates a wreck in which the front corner of the car hits another car or solid object at 40 mph.

“This is the first time that we know of that a manufacturer has called back vehicles after making a structural change like this to improve crash-test performance,” said Russ Rader, spokesman for the insurance industry group.

In the first test, the Fit received a “marginal” rating.

Other automakers, including Honda, have called back cars after IIHS crash tests revealed flaws in their vehicles. But those cases involved airbags that could be reprogrammed, or fuel system parts that could be strengthened to prevent leaks — relatively easy changes to make, Rader said.

The bumper replacement “is unprecedented,” said Scott Oldham, editor of car-shopping website Edmunds.com. “It speaks to the company’s appreciation for proactively doing right by its customers from a safety perspective. No company wants to be on the wrong end of that story in this day and age.”

Technically not a recall — failing an IIHS crash test does not imply a specific safety defect that triggers action by the National Highway Traffic Safety Administration — the bumper problem represents the type of issue that automakers have become increasingly sensitive to in recent years.

Car companies have recalled more than 46 million vehicles in the U.S. this year. That’s almost one of every five cars in the U.S. and eclipses the annual recall record of 30.8 million vehicles set in 2004.

The wave of recalls comes as Toyota, GM and Hyundai all have paid large federal fines for failing to recall vehicles promptly in previous years. GM remains the target of NHTSA and Justice Department investigations for not previously recalling cars with an ignition-key defect now linked to at least 13 deaths and more than 50 crashes.

Honda maintains that the Fit was safe even before the bumper change, noting that it did well on other crash tests. But the automaker said it didn’t believe it was fair to have customers penalized for buying an early 2015 model year Fit, built before June 9, when the company incorporated the bumper change at the Celaya, Mexico, factory where the subcompact is assembled.

“This is not a small undertaking, but the action underscores Honda’s long-term commitment to safety,” said Chuck Thomas, the automaker’s chief engineer for vehicle safety in the U.S.

Honda can retrofit the existing cars because an analysis of the crash-test results found the problem in a steel beam behind the plastic covering of the front bumper.

When it designed the car, Honda said, it believed the beam was strong enough to deflect the crash energy from the front corner of the vehicle to the side that was not struck. This would reduce the intrusion of the vehicle’s structure into the passenger cabin.

But in the first test of the Fit, the bumper beam broke because the welds didn’t hold properly, the company said. The new beam has stronger welds that hold the bumper together and better distribute the crash energy, Thomas said.

Fit owners will be contacted by Honda with instructions to take their vehicles back to dealers for the change. Service departments will remove the plastic covering, unbolt the old beam and replace it with the improved bumper. Thomas said the change would require about 30 minutes of labor.

The insurance institute urged Fit owners to take advantage of Honda’s replacement program.

The organization, which analyses vehicle safety issues for the insurance industry, has been crash-testing vehicles for nearly two decades. Over the years, its test results and safety ratings have become increasingly influential. Consumer Reports, for example, has removed vehicles from its recommended list after they have failed the IIHS small overlap crash test.

Car companies often advertise the results when their vehicles score high. They also make changes in subsequent generations of vehicles that score poorly, in order to do better in the tests.

Positive ratings also affect sales, said David Zuby, the institute’s executive vice president.

A survey by IIHS found that, following the announcement of small overlap crash test ratings, dealers who had vehicles that did well on the test saw more traffic and sold more cars.

“That suggests that some consumers are hearing the message and acting on it by seeking the vehicles we have named as safe,” Zuby said.