Realizing that a non-moving car is a useless car, Kia and Hyundai have recalled nearly 1.2 million vehicles in the U.S. over concerns about engine failure.

The recall affects 572,000 Hyundai Sonata and Santa Fe Sport vehicles (model years 2013-14).

A total of 618,160 Kia vehicles are being recalled: the Kia Optima (2011-14); Sorento (2012-14); and Sportage (2011-13).

According to notices posted by Hyundai [PDF] and Kia [PDF], the affected vehicles contain Theta engines that may have been improperly manufactured.

The carmakers both agree that machining errors during the engine manufacturing process may have caused metal debris to form inside the engine. As a result, the debris and uneven surface could restrict oil flow to the bearings, causing premature wear.

If this occurs, the engine could seize while the vehicle is in motion, increasing the risk of crash.

The recall is actually the second for Hyundai over the issue. The carmakers recalled 470,000 Sonata vehicles because of debris in the engine in Sept. 2015.

In a chronology [PDF] of the new recall, Kia notes that it began investigating the issue after Hyundai’s initial recall. The company says it noticed a slight increase in warranty claims for certain vehicles, it then extended the warranty coverage, but eventually determined a recall was necessary.

Both carmakers say they will begin notifying owners of the affected vehicles in May. Dealers will inspect the engine assembly, replacing it if necessary.

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