The US National Highway Traffic Safety Administration (NHTSA) has initiated an investigation into 1.4 million Honda vehicles due to serious engine issues.

The NHTSA is conducting a probe to assess the severity of engine problems reported in various Honda and Acura vehicles from the 2016-2020 model years.

This follows Honda's recall of 249,000 vehicles in the US in November 2023, which was prompted by a manufacturing defect in the 3.5-liter V6 engine's crankshaft.

Honda has acknowledged the investigation, stating that it "has already been in communication with the agency on this topic and will continue to cooperate with the NHTSA through the query process."

The automaker had first begun looking into the issue in 2020 and, after several years of investigation, issued a recall.

Under the recall, dealers are tasked with inspecting the vehicles and will repair or replace the engine as necessary.

Honda, last year, reported that it had received 1,450 warranty claims related to the recall.

The NHTSA's current investigation is based on 173 reports of engine failures that are consistent with the issues addressed in the 2023 recall but involve vehicles that were not included.

The probe covers several models, including the Acura MDX, Acura TLX, Honda Pilot, Honda Ridgeline, and Honda Odyssey.

Last month, Honda Motor announced a voluntary recall of approximately 720,000 vehicles due to potential fuel pump leaks.

The US division of the Japanese automaker confirmed that owners of specific 2023-2025 Honda Accord, CR-V Hybrid, and Honda Civic models will be invited for a free inspection.

If any defects are identified, the company will replace fuel pump at no charge.