Honda will call back roughly 12,000 early-production ’15 Fit subcompacts sold in the U.S. to replace their steel front-bumper beam.

The fix, which Honda officially calls a “product update” and says is voluntary on its part, should remedy those models’ poor performance in the Insurance Institute for Highway Safety’s small-overlap front crash test, which replicates a collision with a thin object such as a post.

Much to Honda’s surprise, the ’15 Fit was rated by IIHS as just a “marginal” performer, Chuck Thomas, chief engineer-vehicle safety, tells media in an Aug. 20 conference call.

“It’s a very demanding test and it puts a lot of stress on the vehicle’s structure,” he says as to why the subcompact didn’t do as well as expected.

Honda’s downfall was welding, he says, noting the automaker later discovered the bumper connection between the left and right sides of the engine wasn’t strong enough.

The free bumper-beam replacement to Fits already on the road is “easily done within 30 minutes,” Thomas says, requiring removal of the Fit’s bumper cover and some bolts that hold on the existing beam.

The silver lining for Honda is, after strengthening welds in a running change made June 9, the Fit now scores “acceptable” on the IIHS small-overlap test, helping the car earn a 2014 Top Safety Pick designation by IIHS.

Honda builds the Fit at its new plant in Celaya, Mexico, and all early builds of the car were sold in the U.S., says spokeswoman Robyn Eckard-Eagles.

In late September, American Honda will be notifying owners of affected ’15 Fits that they will need to bring their vehicle in for service.

cschweinsberg@wardsauto.com