Why is the feature not available (lane markings are gray) when I can see the lane markings on the road?  
Your vehicle speed is less than 40 mph (65 km/h).  
The sun is shining directly into the camera lens.  
A quick intentional lane change has occurred.  
Your vehicle stays too close to the lane markings for an extended interval of time.  
Driving at high speeds in curves.  
The last alert warning or aid intervention occurred a short time ago.  
Ambiguous lane markings, for example, in construction zones.  
Rapid transition from light to dark, or from dark to light.  
Sudden offset in lane markings.  
ABS or AdvanceTrac™ is active.  
There is a camera blockage due to dirt, grime, fog, frost or water on the windshield.  
You are driving too close to the vehicle in front of you.  
Transitioning between no lane markings to lane markings, or vice versa.  
There is standing water on the road.  
Faint lane markings, for example, partial yellow lane markings on concrete roads.  
Lane width is too narrow or too wide.  
You have not calibrated the camera after a windshield replacement.  
Driving on tight or on uneven roads.  

Why does the vehicle not come back toward the middle of the lane, as expected, in the Aid, or Aid + Alert mode?  
High cross winds are present.  
There is a large road crown.  
Rough roads, grooves or shoulder drop-offs.  
Heavy, uneven loading of the vehicle or improper tire inflation pressure.  
You changed the tires or modified the suspension.