Sorry, the NHTSA has not posted this TSB document yet.
You can still get the detailed info from Chevrolet for this TSB. Call your local Chevrolet dealer's service department & ask for a copy of TSB# 17-NA-314.
Intermittent Service Power Brake Assist Message With a Brake Shudder and Possible DTC P0557 Set/Stored
Condition
Customer may comment of an intermittent "Service Power Brake Assist" message which
may be accompanied by a brake shudder.
During diagnosis a technician may find DTC P0557 set or stored.
Cause This condition may be caused by the Power Brake Booster Vacuum Sensor providing intermittent incorrect vacuum values due to circuit board fault.
Correction Replace Power Brake Booster Vacuum Sensor & Hose Assembly.
