Pedestrian Impact Detection System Description and Operation

The pedestrian impact detection systems primary function is to provide supplemental protection to vulnerable road users involved in vehicle impacts. The pedestrian impact detection system is also known as the active pedestrian protection system. The pedestrian impact detection system is a functional system for raising the hood to provide sufficient vertical deformation space under the hood. In Europe and Japan an active pedestrian impact detection system is necessary for vehicles which do not provide the required deformation space under the hood. The pedestrian impact detection system includes the following components

• Inflatable Restraint Sensing and Diagnostic Module
• Pedestrian Impact Detection Sensor - Upper Beam Front Left
• Pedestrian Impact Detection Sensor - Upper Beam Front Right
• Two Hood Hinge Actuators

The pedestrian impact detection system will sense and discriminate vulnerable road user impacts and deploy the hood hinge actuators to lift the rear section of the hood in a timely manner to help reduce pedestrian head injuries. The term "deployment" applies to the activation of the hood via the hood actuators. The pedestrian impact detection system is designed to sense and discriminate road user impacts (e.g. pedestrian, cyclist) from other types of impacts in order to properly deploy the hood actuators. No actions or inputs are required from the driver or passenger to trigger this device. The Inflatable Restraint Sensing and Diagnostic Module uses two Pedestrian Impact Detection Sensors connected together by a tube to get force information needed for the deployment of the hood hinge actuators. The Inflatable Restraint Sensing and Diagnostic Module deploys the hood actuators using two deployment loops. The pedestrian impact detection system only operates at vehicles speeds between 22 km/h (14 mph) to 50 km/h (31 mph). The Inflatable Restraint Sensing and Diagnostic Module detects internal and interface faults and commands the Service Pedestrian Protection System message in the driver information center to indicate a system fault.

After a deployment event, the vehicle operator is able to reset the hood to its normal driving position. Refer to the Owner's Manual for more information. After resetting the hood, the pedestrian impact detection system is not required to be fully functional. For full functionality, it is necessary to replace system component(s) at an approved service facility.

Pedestrian Impact Detection Sensors 

The K36 Inflatable Restraint Sensing and Diagnostic Module provides a two wire current loop interface to the Pedestrian Impact Detection Sensor - Right Front and Pedestrian Impact Detection Sensor - Left Front. The Inflatable Restraint Sensing and Diagnostic Module also provides power and ground to the sensors over the same two wire discrete interface. The two sensors are connected together by a tube and are serviced as an assembly.

If the sensors are replaced, visually inspect the front fascia and front bumper fascia energy absorber for cracks or other damage that may interfere with proper operation of the system. Replace any damaged parts.

Hood Hinge Actuators 

The pedestrian hood actuators deploy only when a valid signal whose energy is capable of triggering deployment of the hood is present. The pedestrian hood actuators only deploy in those events where the activation of the hood is expected. The hood actuator is not expected to deploy in low severity event where the risk of injury is low or in a high severity event like car to car crash. During a frontal pedestrian impact of sufficient force, the Inflatable Restraint Sensing and Diagnostic Module will allow current to flow through the deployment loops in order to deploy the hood hinge actuators. The Inflatable Restraint Sensing and Diagnostic Module also performs continuous diagnostic tests on the deployment loops to check for proper circuit continuity, shorts to ground and shorts voltage. In order to prevent unwanted deployment of the actuator during service, the hood hinge actuator contains 2 shorting bars that will short both high and low circuit pins when disconnected. The Inflatable Restraint Sensing and Diagnostic Module only issues a deployment command when a valid Pedestrian Impact Detection Sensor signal or confirmation has been generated. No inadvertent deployments will occur in any deployment loop due to a single point fault.