abs brakes on 03 w9

The whole ABS system works by releasing air to a 'braked' wheel ergo if the brakes are not applied this problem cannot be caused by the ABS system. Do you have a traction control system? Anti-roll? In the absence of an audible air leak or mechanical issue, these 2 are the more likely culprits.

 

give me your ser number, let me see what this truck had from the factory.

 

I had the same problem but my brakes applied and wouldn't release at all! We found the problem being there is a ABS valve on each side of the rear suspension between the drives that supplies the air to the brake chambers and the electronic on the valve went bad and locked the brake! you could possible have 1 of those going bad! the cost of that valve is around 300.00 and they are not hard to change!