If this condition occurs frequently, the rear brake line could be damaged, which could result in leakage of brake fluid, causing a decrease in brake effectiveness.
Service Brakes, Hydraulic — Foundation Components — Hoses, Lines/Piping, And Fittings
On certain passenger vehicles, if the vehicle is driven under repeated start and stop operation in low ambient temperatures and in deep snow, there is a possibility that snow could accumulate in large quantities inside the rear wheel and freeze. The snow frozen inside the wheel could contact the rear brake line during wheel rotation.
Dealers will replace the rear brake lines. Owner notification began November 9, 2002. Owners who take their vehicles to an authorized dealer on an agreed upon service date and do not receive the free remedy within a reasonable time should contact Toyota at 1-800-331-4331.