Jeep 2011 Grand Cherokee Owner's Manual page 117

UNDERSTANDING THE FEATURES OF YOUR VEHICLE 115
Overtaking Traffic
If you pass another vehicle slowly (with a relative speed
less than 10 mph (16 km/h) and the vehicle remains in
the blind spot for approximately 1.5 seconds, the warning
light will be illuminated. If the difference in speed
between the two vehicles is greater than 10 mph
3
(16 km/h), the warning light will not illuminate.
Overtaking/Passing
Overtaking/Approaching