Horn
Pressa 
on the steering wheel pad
to sound the horn.
See also:
How the System Works
URPA comes on automatically when the shift lever is moved into R (Reverse). A single tone sounds to indicate the system is working.
URPA operates only at speeds less than 8 km/h (5 mph).
An obstacle ...
How to Check Lubricant
2500HD with 6.0 L
All Other Series and Engines
To get an accurate reading, the vehicle should be on a level surface.
• For all 4.3 L, 4.8 L and 5.3 L 1500 Series applications, the proper leve ...
Retrieve My Number
1. Push X. System responds: “OnStar ready.”
2. Say “My Number.” System responds: “Your OnStar Hands-Free Calling number is.” ...