Buick Brake Relay Isn't Seated
Some owners of 2016 Buick Lacrosse or Regal vehicles may comment on a hard brake pedal on a cold startup and/or a service brake assist message.
The technician may find DTC C027B or P050F set in the BCM. On some vehicles, the connector at the KR14 brake booster pump motor relay was not fully seated.
Note that the brake booster pump relay is incorporated into the brake booster pump motor. If the connector is not fully seated, press the connector fully into the cavity.
After seating the connector, deplete brake booster vacuum by pressing the brake pedal several times with the engine off and then restart the engine and confirm that the brake booster pump runs and there is normal brake pedal function.