The official notice
Defect
Certain vehicles do not comply with the requirements of CMVSS 121 - Air Brake Systems. The air brake system was plumbed so that complete air reservoir isolation was not provided. Some vehicles were built with an air line from the system ECU Relay Valve Module tee fitting, incorrectly connected to the system supply tank, rather than the system auxiliary primary tank. A leakage or failure can cause a pressure loss in the secondary tank resulting in the draining of the primary tank also, and thus a complete loss of vehicle system air pressure, diminishing brake effectiveness, and increasing the risk of a crash.
Safety Risk
No risk description available.
Remedy
Dealers will inspect the vehicle to determine whether the vehicle has the incorrectly routed air line. Those with the condition will be correctly plumbed and the air brake system tested to verify proper reservoir isolation.