A House of Councilors committee endorsed on Tuesday a proposed legal revision that would include child seats as subject to recall for free repairs under the Road Trucking Vehicle Law.
Tires and other parts added to finished vehicles would also be subject to the measure.
The bill, unanimously approved by the Upper House's Land and Transport Committee, was expected to pass a plenary session of the Upper House on Wednesday.
The amendment would increase the maximum fine to 200 million yen, up from the current 200,000 yen, for automakers that fail to recall vehicles with defects or try to cover up defects.
In addition, the amendment would punish vehicle owners who make illicit modifications to cars.