Audi Korea has issued a voluntary recall campaign for more than 9,000 of its 2013-2015 model A4 and S4 vehicles for faulty frontal airbags, the carmaker said Friday.

The recall models are the A4 2.0 TDI (8,055 units), A4 2.0 TFSI (977 units) and S4 3.0 TFSI (59 units) that were manufactured from March 2013 to mid-October 2014, adding up to 9,091 vehicles.

The voluntary recall campaign comes after the discovery that the airbags were not properly inflating during accidents due to an error in the airbag control unit.

The company said it would correct the problem by offering free check-ups and control unit software updates. The updates will take about half an hour. 

These services will be provided at 24 Audi car service centers nationwide, and the campaign will run until May 20, 2016.

Audi Korea has been sending out individual notices to related clients via mail through the Korea Automobile Testing & Research Institute and will continue to do so, the automaker said.

(baejisook@heraldcorp.com)