See also:

Tachometer
The tachometer displays the engine speed in revolutions per minute (rpm). ...

Adjusting the EQ (Equalizer)
For vehicles with an equalizer: 1. Press the TONE button. 2. Select EQ. 3. Select the setting. Press the BACK button to go back to the Tone Settings menu. ...

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. Added electrical equipment may interfer ...