Downloaded the manual and can add more information here if anyone is interested and unaware:
The Pop Up Hood will operate when the vehicle detects an impact such as the following: The front bumper detects a frontal impact equivalent to or greater than that of a pedestrian while the vehicle being driven within the operational speed range of approximately 25 to 55 km/h (16 to 34 mph). (The system is operated by an impact of threshold level or greater, even in the case of a minor collision that may not leave a trace on the front bumper. Also, depending on the impact conditions or vehicle speed, the system may be operated by a collision with a light or small object or a small animal.)
In other situations the system may operate when an impact is applied to the lower part of the vehicle or front bumper, such as the following:
Colliding with a curb
Falling into a deep hole
Landing hard
Hitting the slope of a parking lot, an undulating road, a protruding object or falling object
The Pop Up Hood may not operate properly under the following conditions:
If a pedestrian collides with the right or left corner of the front bumper or the side of the vehicle. As such impacts may be difficult to detect, the system may not operate.
If the vehicle speed is not detected correctly, such as if the vehicle is sliding sideways, the system may not operate properly.
Conditions under which the Pop Up Hood may not operate The Pop Up Hood may not operate in the following situations:
Colliding with a lying pedestrian
A frontal impact applied to the front bumper while driving at speeds outside of the operational speed range
A side impact or rear impact
A vehicle rollover (In some accident situations, the Pop Up Hood may operate.)
Pop Up Hood precautions
Make sure to close the hood before driving, as the system may not operate properly if the hood is not fully closed.
Make sure that all 4 tires are of the specified size and inflated to the specified tire pressure (P. 544). If tires of a different size are used, the system may not operate properly.
If something has hit the area around the front bumper, the sensors may be damaged even if the Pop Up Hood has not operated. Have the vehicle inspected by any authorized Lexus dealer or repairer, or another duly qualified and equipped professional.
Do not remove or repair the parts or wiring of the Pop Up Hood, as doing so may cause accidental operation or prevent the system from operating properly. If repair or replacement is necessary, contact any authorized Lexus dealer or repairer, or another duly qualified and equipped professional.
Do not remove such components as the front bumper, hood or suspension, or replace them with non-genuine parts, as doing so may prevent the system from operating properly.
Do not install anything to the front bumper or hood, as doing so may prevent the sensors from detecting an impact correctly and prevent the system from operating properly.
Do not close the hood with force or apply load to the lifters, as doing so may damage the lifters and prevent the system from operating properly.
Do not modify the suspension, as changes made to the vehicle height may prevent the system from operating properly