General Motors Co. is recalling 3.46 million U.S. pickup trucks and SUVs to address a vacuum pump issue that could make braking more difficult and increase the risk of a crash.

The recall, which covers 2014-2018 model year vehicles, including some Cadillac Escalade, Chevrolet Silverado, Chevrolet Tahoe, GMC Sierra, Chevrolet Suburban and GMC Yukon vehicles, was triggered because the amount of vacuum created by the vacuum pump may decrease over time, GM told the National Highway Traffic Safety Administration (NHTSA) in documents posted Wednesday.

NHTSA opened a preliminary investigation into the issue in November 2018, and said it had reports of 9 crashes and two injuries related to the issue. It provided GM in July with additional field reports that prompted the automaker to open an investigation.

The company did not immediately say on Wednesday how many injuries or crashes are linked to the issue but said it could impact braking in "rare circumstances."

GM said dealers will reprogram the Electronic Brake Control Module with a new calibration that will improve how the system utilizes the hydraulic brake boost assist function when vacuum assist is depleted.

GM said the vacuum assist pump, which is lubricated with engine oil that flows into the pump through a filter screen, can in some cases lose effectiveness over time, as debris such as oil sludge can accumulate on the filter screen.

GM told NHTSA that prior model years used a different brake assist system design, and vehicles manufactured after 2018 were not equipped with the affected pump design.