Braking Problems - Stabiltrac / Traction Control System

[STANLEY]

2 error messages popped up on same day, back to back:  Service Stabiltrac and Service Traction Control System.  Very shortly after this the brake pedal got hard and the brakes begin to apply on their own [no driver input] to the point where I could no longer drive the vehicle, had to stop.  All of this happened within a 5 min period.  The GMC dealer has had truck for a week, worked with the factory, and finally had the dealer do following:

• Put truck on lift, start engine
• step on gas to simulate driving
• when messages popped up and truck started self-braking, lift up on the brake pedal
• If this cured the issue, factory said the brake booster must be replaced.  If lifting the pedal had not cured the issue, then the master cylinder had to be replaced.
•  

Dealer replaced the booster, took the truck on a drive, and issue repeated itself.  Back to factory again Monday.  Dealer has not seen this issue before.

 

Has anyone experienced this??

John

[STANLEY]

I neglected to mention that this same GMC dealer replaced the mechanical diaphragm under a Special Allowance program for the 2017 Sierra paid for by GMC.  The self-braking symptom started about 1 week after the diaphragm work was completed.