The hand valve installed in the vehicle may have been incorrectly positioned. This would allow air to escape from both the front and rear service systems simultaneously if the control line to the rear axle relay valves should fail. Performance of front and rear service brakes during failure could be degraded.
Risk and remedy
Remedy
The hand valve will be repositioned by the dealer, if necessary, at no charge owner.
Some of the involved vehicles do not comply with federal motor vehicle safety standard no. 121, "air brake systems". The air reservoir capacity IS below that allowed by the standard.
Risk and remedy
Remedy
Dealer will either replace the existing tank with a larger tank or add a second tank, without charge to owner.