Jeep Grand Cherokee 2013 Owner's Manual page 244

242 UNDERSTANDING THE FEATURES OF YOUR VEHICLE
The "Clean Radar Sensor In Front Of Vehicle" message
can sometimes be displayed while driving in highly
reflective areas (i.e. tunnels with reflective tiles, or ice and
snow). The ACC system will recover after the vehicle has
left these areas. Under rare conditions, when the radar is
not tracking any vehicles or objects in its path this
warning may temporarily occur.
Clean Radar Sensor Warning
NOTE: If the ACC "Clean Radar Sensor In Front Of
Vehicle" warning is active Normal (Fixed Speed) Cruise
Control is still available. For additional information refer
to "Normal (Fixed Speed) Cruise Control Mode" in this
section.