Description
Pedestrian Protection System
NOTE:
A = Hardwired; D = High speed CAN (controller area network) bus.
PRINCIPLES OF OPERATION
The pedestrian protection system is operational when the vehicle is traveling at speeds between approximately 20 and 45 km/h (12.4 and 28 mph). A vehicle speed signal is received by the RCM (restraints control module) over the high speed CAN (controller area network) bus.
The system is able to determine if contact is made with a pedestrian or another object, such as a traffic cone, using signals from the pedestrian impact sensors. When the system determines contact is made with a pedestrian, it fires the hood actuators to lift the rear of the hood approximately 130 mm (5.2 in.) within 35 ms of the 'fire' signal.
When an impact condition is registered, the RCM (restraints control module) outputs an impact signal on the high speed CAN (controller area network) bus. This signal is used by the CJB (central junction box) to initiate the hazard warning lamps. If this occurs, the hazard warning lamp switch is disabled for the remainder of the current ignition cycle.
If the RCM (restraints control module) detects a fault with the system, it outputs a message on the high speed CAN (controller area network) bus to the instrument cluster message center. On receipt of this, the message center will display the message Check Pedestrian System.
When the vehicle is delivered from the factory the pedestrian protection system is in a safe 'plant' mode. Normal operating mode must be activated using Jaguar approved diagnostic equipment during the PDI (pre-delivery inspection) prior to delivery to the customer.
Failure Mode Detection
In service, if any fault is detected, the message center displays the warning Check Pedestrian System.
The hood deployment actuators are non-serviceable components. If they are replaced their bar code labels must be read and recorded in the service database against the VIN (vehicle identification number) for security purposes.
After deployment of the pedestrian protection system, the vehicle must be stopped as soon as it is safe to do so. The hazard warning lamps will be activated and can only be switched off by pressing the engine START/STOP button to turn the engine off and on again. A warning message Check Pedestrian System will appear in the message center and the vehicle should be transported to the nearest dealer/authorized repairer. The vehicle must not be driven when the hood has been deployed.
HOOD ACTUATORS
The hood actuators are pyrotechnic air bags installed on mounting brackets next to the hood hinges. When the hood actuators are deployed, interface plates on the actuators contact reinforced areas on the hood, and raise the rear of the hood.
PEDESTRIAN IMPACT SENSORS
The pedestrian impact sensors are accelerometers mounted on the rear of the front bumper. The RCM (restraints control module) uses the sensor inputs to monitor for low level impacts typical of pedestrian accidents.
HOOD
The two-piece hood is fabricated from aluminum. The inner panel has a hexagonal structure, which allows the energy from an impact to be absorbed effectively across the full area of the hood. The hood also has sufficient strength in the rear cross-beam to accept the forces from the actuators and maintain a stable condition.
When deployed, the front hood latches act as the pivot points and the rear hinges allow a controlled degree of upward movement before retaining the hood at the end of its deployment, thus limiting its total upward travel and stabilizing its position.
Hood Hinges
The hood hinges incorporate a number of leaves. This includes a leaf attached to the body, an intermediate leaf and a leaf attached to the hood. During normal operation the hinge opens and closes using the hood and intermediate leaves. These are attached together by a firing pin. When the actuators are fired the firing pins fail. This allows the hood and intermediate leaves to separate and deploy the hood upwards.
The hinges deform during the deployment process and will need to be replaced.