Ford Kuga

 Service Manual

Supplemental Restraint System » Air Bag and Safety Belt Pretensioner Supplemental Restraint System (SRS) (System Operation and Component Description)
System Operation

When the ignition is switched on the restraints control module (RCM) supplies power to the crash sensors, which perform a self-diagnosis.

The crash sensors are located at the front of the vehicle and on both sides. Once the self-diagnosis has been successfully completed, the crash sensors continuously send acceleration data to the RCM. The use of multiple crash sensors optimizes airbag deployment times through faster detection of lateral and longitudinal acceleration and improves detection accuracy. Each crash sensor has an accelerometer which receives a current supply from the RCM. The acceleration is transmitted to the RCM, which then makes the decision on whether or not to activate the airbags and pretensioners. In the event of a fault, the affected crash sensor sends an error message to the RCM instead of the acceleration data. The RCM then stores a related fault code and illuminates the air bag warning indicator.

Triggering process The front airbags are designed so that they are not triggered in a side or rear impact if they do not offer additional protection to the occupant(s). In exceptional cases, the front air bags can be deployed even by a side impact if the forward motion of the vehicle suddenly comes to a complete stop. Airbags and safety belt pretensioners are triggered according to the severity of the impact in an accident. The exact triggering threshold is determined with the aid of a triggering algorithm which is specially calibrated for the vehicle. This algorithm contains triggering thresholds, which - when exceeded - cause the necessary restraint systems to be deployed according to the severity of the accident. When an impact occurs the airbag is inflated within approx.

30 milliseconds. The occupant reaches maximum immersion in the air bag after 80 ms. Emptying of the fully-inflated bag takes approx. 100 ms. The entire impact and energy absorption process is completed after approx.150 ms. The system triggers the safety belt pretensioners first. In a more severe accident the front airbags are also deployed. In a side impact, the relevant side air bag and side air curtain are deployed by the RCM, provided the severity of the side impact is such that the side air bag/side air curtain offers the occupant additional protection. Deployment is triggered on the basis of a signal input from the left or right crash sensor.

System Diagram

System Operation

Component Description