Mercedes-Benz C-Class Manuals

Mercedes-Benz C-Class (W205) 2015 - 2021 Owners Manual: Restraint system

Protection by the restraint system

The restraint system includes the following components:

  • Seat belt system
  • Airbags
  • Child restraint system
  • Child seat securing system

The restraint system can reduce the risk of vehicle occupants coming into contact with parts of the vehicle's interior in the event of an accident.

The restraint system can also reduce the forces to which vehicle occupants are subjected in the event of an accident.

Only a seat belt which is worn correctly can provide the intended level of protection. Depending on the detected accident situation, Emergency Tensioning Devices and/or airbags supplement a correctly worn seat belt. Emergency Tensioning Devices and/or airbags are not deployed in every accident.

For the restraint system to provide its full protection, each occupant must observe the following:

  • Fasten the seat belt correctly.
  • Be in an almost upright position with their back against the seat backrest.
  • Sit with their feet resting on the floor, if possible.
  • Always secure persons under 5 ft (1.50 m) tall in an additional restraint system suitable for Mercedes-Benz vehicles.

However, no system available today can completely eliminate injuries and fatalities in every accident situation. In particular, the seat belt and airbag generally do not protect against objects penetrating the vehicle from the outside.

The risk of an injury resulting from airbag deployment also cannot be ruled out entirely.

Limited protection from the restraint system

WARNING Risk of injury or death from modifications to the restraint system
The restraint system can no longer function correctly after alterations have been made.

The restraint system may then not protect the vehicle occupants as intended by failing in an accident or triggering unexpectedly, for example

  • Never alter the parts of the restraint system.
  • Never tamper with the wiring or any electronic component parts or their software.

If it is necessary to adjust the vehicle to accommodate a person with disabilities, contact an authorized Mercedes-Benz Center for details.

USA only: for further information contact our Customer Assistance Center at 1-800-FOR-MERCedes (1‑800‑367‑6372).

Restraint system functionality

When the ignition is switched on, a self-test is performed, during which therestraint system warning lamp lights up. It goes out no later than a few seconds after the vehicle is started.

The components of the restraint system are then functional.

Malfunctioning restraint system

A malfunction has occurred in the restraint system if:

  • therestraint system warning lamp does not light up when the ignition is switched on
  • therestraint system warning lamp lights up continuously or repeatedly during a journey
WARNING Risk of injury or fatal injury due to a malfunction in the restraint system
If the restraint system is malfunctioning, restraint system components may be triggered unintentionally or might not be triggered at all in the event of an accident. This may affect the Emergency Tensioning Device or airbag, for example.
  • Have the restraint system checked and repaired immediately at a qualified specialist workshop.

Function of the restraint system in an accident

How the restraint system works is determined by the severity of the impact detected and the type of accident anticipated:

  • Frontal impact
  • Rear impact
  • Side impact
  • Rollover

The activation thresholds for the components of the restraint system are determined based on the evaluation of the sensor values measured at various points in the vehicle. This process is preemptive in nature. The triggering/deployment of the components of the restraint system must take place in good time at the start of the collision.

Factors which can only be seen and measured after a collision has occurred do not play a decisive role in the deployment of an airbag. Nor do they provide an indication of airbag deployment.

The vehicle may be deformed significantly without an airbag being deployed. This is the case if only parts which are relatively easily deformed are affected and the rate of vehicle deceleration is not high. Conversely, an airbag may be deployed even though the vehicle suffers only minor deformation. If very rigid vehicle parts such as longitudinal members are hit, for example, this may result in sufficiently high levels of vehicle deceleration.

The components of the restraint system can be activated or deployed independently of each other:

Component Detected deployment situation
Front Emergency Tensioning Devices Frontal impact, rear impact, side impact, rollover
Rear Emergency Tensioning Devices Frontal impact, rear impact, rollover
Driver's airbag, front passenger front airbag Frontal impact
Knee airbag Frontal impact
Side airbag Side impact
Window curtain airbag Side impact, rollover, frontal impact

The front passenger front airbag can only be deployed in an accident if the PASSENGER AIR BAG OFF indicator lamp is off. If the front passenger seat is occupied, make sure, both before and during the journey, that the status of the front passenger front airbag is correct.

WARNING Risk of burns from hot air bag components
The air bag parts are hot after an air bag has been deployed.
  • Do not touch the air bag parts.
  • Have a deployed air bag replaced at a qualified specialist workshop as soon as possible.

Mercedes-Benz recommends that you have the vehicle towed to a qualified specialist workshop after an accident. Take this into account, particularly if an Emergency Tensioning Device is triggered or an airbag deployed.

If the Emergency Tensioning Devices are triggered or an airbag is deployed, you will hear a bang, and a small amount of powder may also be released:

  • The bang will not generally affect your hearing.
  • In general, the powder released is not hazardous to health but may cause short-term breathing difficulties to persons suffering from asthma or other pulmonary conditions.

    Provided it is safe to do so, leave the vehicle immediately or open the window in order to prevent breathing difficulties.

Airbags and pyrotechnic Emergency Tensioning Devices contain perchlorate material, which may require special handling or environmental protection measures. National guidelines regarding waste disposal must be observed. In California, see Perchlorate/index.cfm.

    Occupant safety

    Seat belts

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