Volvo Trucks North America (Volvo Trucks) is recalling 2021 VNL, VNR, VAH, and VHD vehicles. The collets (internal jaws) for the brass fitting inserts used in the pneumatic pass-through plate may have been damaged during leak testing. As a result, the brass fitting may completely release the air brake line from the pass-through plate while under pressure. If this occurs on the park brake circuit, signal pressure that holds off the mechanical spring in the park brake chambers will be lost allowing the park brakes to apply.