Jeep Grand Cherokee 2013 Owner's Manual page 133

UNDERSTANDING THE FEATURES OF YOUR VEHICLE 131
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
3
between the two vehicles is greater than 10 mph
(16 km/h), the warning light will not illuminate.
Overtaking/Passing
Overtaking/Approaching