4 million Honda and Acura vehicles. This inquiry primarily concerns models equipped with 3.5-liter V6 engines, including the 2016–2020 Honda Pilot and Acura MDX, the 2018–2020 Honda Odyssey and Acura TLX, and the 2017–2019 Honda Ridgeline.

Documents released by the agency on Monday reveal that the connecting rod bearings on these vehicles are prone to failure, which can lead to total engine breakdown. Connecting rods are crucial components that link pistons to the crankshaft, facilitating the conversion of vertical motion into the rotational force needed to drive the wheels.

In November 2023, Honda had already recalled about 250,000 vehicles to address this specific issue. However, the NHTSA has received 173 additional complaints from vehicle owners reporting connecting rod bearing failures in models not covered by the initial recall. One such complaint even detailed a crash incident, although fortunately, no injuries were reported.

The NHTSA has now opened a formal recall query to assess the extent of the problem in the vehicles excluded from the 2023 recall. Honda has pledged to cooperate fully with the investigation.

In the documentation related to the recall last year, Honda reported 1,450 warranty claims due to the bearing issue but noted that no injuries had been associated with these failures. As part of the recall, dealers were tasked with inspecting, repairing, or replacing the engines as necessary.