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Complaints of locked parking brakes have been addressed via a service campaign rather than a safety recall.

The National Highway Traffic Safety Administration has closed its investigation into complaints of brake problems with the Hyundai Sonata.The agency identified at least four reports alleging the rear brakes locked or applied while driving, without any brake pedal application. One report claimed a locked brake created a fire in the right rear wheel area.

Vehicles subject to the investigation all use an electronic parking brake (EPB) system activated by a control switch. It is released either by the switch or automatically disengaged when the vehicle is shifted out of 'park' when the ignition is on.

The NHTSA suggests the EPB system performs an automatic adjustment function to check pad clearance if the EPB has not been used in the first 1000 kilometers. The Sonata apparently suffered from an error within the EPB control logic that caused the pads to remain in contact with the rotors after the adjustment cycle has finished.

"This condition could cause the rear brakes to drag at the next drive cycle and may generate some levels of heat and smoke," the agency says. "There are no reports of accidents or injuries as a result of this issue. The incident that alleged fire could not be confirmed as there were no repairs to the vehicle other than replacement of the rear brake rotors and pads."

Hyundai has implemented a software fix to address the behavior. Without any accidents or injuries, the NHTSA apparently does not believe a recall is warranted.
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