Fiat Chrysler Automobiles NV’s (FCHA.MI) U.S. arm, said it was voluntarily recalling about 646,394 SUVs in the United States to check shields that protect brake boosters for proper installation.

FCA US was aware of a single potentially related accident, the company said on Tuesday.

The shields are designed to protect the boosters from corrosion caused by water exposure. In case a booster is compromised by water it would cause excessive brake-pedal firmness, the company said.

The shields were originally installed in conjunction with a 2014 recall involving the same set of vehicles, nearly 95 percent of which have been serviced, the automaker said.

The affected vehicles are model-year 2011-2014 Dodge Durango and Jeep Grand Cherokee SUVs.