See also:

Add-on Electrical Equipment
The OnStar system is integrated into the electrical architecture of the vehicle. Do not add any electrical equipment. See Add-On Electrical Equipment on page 9‑64. Added electrical equipment ...

Horn
Press on the steering wheel pad to sound the horn. ...

How to Add Coolant to the Coolant Surge Tank for Gasoline Engines
If the vehicle has a diesel engine, see “Cooling System” in the Duramax Diesel Supplement for the proper coolant fill procedure. WARNING You can be burned if you spill coolant on hot engine part ...