Incorrectly Installed Quick Release Valve/FMVSS 121

PACCAR Incorporated (PACCAR) is recalling certain 2026-2027 Peterbilt 579 and 2027 Kenworth T680 tractors. The trailer air connection quick release (QR) valve in the air brake system may have been incorrectly installed, which can cause the trailer to become unstable after the driver applies the brakes. As such, these vehicles fail to comply with the requirements of Federal Motor Vehicle Safety Standard number 121, "Air Brake Systems."