See also:

Horn
Press near or on the horn symbols on the steering wheel pad to sound the horn. ...

Reporting Safety Defects to General Motors
In addition to notifying NHTSA (or Transport Canada) in a situation like this, please notify General Motors. Call 1-800-521-7300, or write: Buick Customer Assistance Center P.O. Box 33136 ...

Ultrasonic Parking Sensor Light
This light comes on to indicate that there is a malfunction in the system. See your dealer for service. See Ultrasonic Parking Assist  and Driver Information Center (DIC)  for more infor ...