The brake assist malfunctioned causing the brakes to abruptly stop without cause or warning. When the braking system abruptly stopped it caused a jack knife and lost of a trailer on a congested highway with vehicles in all lanes, I was able to finally get control of the tractor with out causing contact or injury with other vehicles and the rear trailer broke free and rolled back and landed in the grass that divided the highways. I injured myself and had to have surgery. The tractor was taken to a shop 4 days after the accident. They found that the module for abs ec80 had blocked radar and data link faults for camera, radar & camera was not properly installed. Rush truck center told the company that they needed to drive tractor on a long drive to recreate issues, but the company denied to go forward and picked the tractor up.