Jeep 2011 Grand Cherokee Owner's Manual page 197

UNDERSTANDING THE FEATURES OF YOUR VEHICLE 195
The system will indicate a detected obstacle by showing
three solid arcs and will produce a one-half second tone.
As the vehicle moves closer to the object the EVIC
display will show fewer arcs and the sound tone will
change from slow, to fast, to continuous.
3
Fast Tone
Slow Tone