- a) two front (frontal) airbags are standard. The driver's airbag module is housed in the steering wheel hub. The front passenger airbag is placed in a special cavity on the right side of the car's instrument panel. The locations of both cushions are marked with warning labels «SRS AIRBAG»;
- b) Two side airbags for the front seats are standard. The side airbag modules are integrated into the outer side portions of the seatbacks;
- With) head pillows (curtains) security (additional equipment) , located along the side edges of the ceiling panel and providing additional protection for the heads of the driver and all passengers in case of side impacts and vehicle rollover;
- d) Directional g-force sensors, triggered by a strong frontal / side impact;
- e) Electronic self-diagnosis system, which, with the ignition on, provides continuous testing of overload sensors, the control unit, airbag gas generators and the connecting wiring of the corresponding circuits;
- f) Automatic emergency tensioners for front seat belts are standard;
- g) SRS warning lamp built into the instrument panel;
- h) Spare stand-alone power supply, designed to duplicate the main power system in the event of its failure in a car collision.
A special SRS warning lamp is built into the dashboard of the car, designed to warn the driver about failures in the additional security system detected by the self-diagnosis system.
Depending on the vehicle's equipment, if the warning light comes on, there may be a problem with the front/side airbag modules or the automatic emergency seat belt tensioners.
The principle of operation of frontal airbags
Attention! Never carry young children in the front seat of a car equipped with a passenger airbag! This also applies to the installation of a special child seat in the front seat.
Attention! In light collisions and rollovers, the front airbags should not deploy.
 |  |
The front airbag modules are mounted in the steering wheel hub and in the panel on the right side of the instrument panel, directly above the main glove box.
Directional g-force sensors respond to exceeding a certain limit value that may occur in a severe frontal collision. At the signal of the sensors, the control unit turns on the gas generators of the airbags, causing them to instantly fill.
During a collision, the seat belt keeps the occupant's lower torso from moving. Front airbags help prevent injury to the driver and front passenger from head and chest impacts on the steering wheel/dashboard.
Because the signals to deploy both airbags come from the same sensors, both airbags deploy at the same time. However, the possibility of initiation of only one of the pillows is not ruled out. This becomes possible when the magnitude of the directional overloads that occurred during a collision was on the verge of the sensitivity range of the sensors. In this case, the seat belts provide sufficient protection for the driver and front passenger, while the effect of the airbag deployment will be minimal.
Immediately after the airbags are deployed and perform their functions, gas is released from them, which allows the driver to maintain visibility and freely manipulate all vehicle controls.
The total duration of the process from the moment the signal is given by the overload sensors to the release of gas from the pillows takes a fraction of a second. The airbags deploy so quickly that the human ear is simply unable to perceive the sound of gas generators when the airbags are filled.
After a traffic accident in which the airbags were deployed, the interior of the car looks slightly smoky. In fact, this is a suspension of finely dispersed powder, which is usually sprinkled with pillow shells in the folded state. People with a respiratory disease may experience some discomfort from the airborne gaseous products emitted by airbag generators.
The principle of operation of the side and head airbags
The side airbag modules are installed in the front door panels of the vehicle.
The locations of both side cushions are usually marked with inscriptions «SIDE AIRBAG». Head cushion gas generators are located on the side edges of the ceiling panel.
In case of a strong side impact, the sensors of directional overloads record the excess of the emerging loads of a certain threshold value and issue an information signal to the control unit, which generates a command to deploy the gas generator of the corresponding side airbag.
In this case, if the impact came from the side of the passenger seat, the passenger side airbag will work even if there is no passenger in the front seat.
For the most effective protection from airbags, the driver and front passenger should sit up straight and wear their seat belts.
Order of functioning of a control lamp of failures SRS
When the ignition is turned on (ignition key turned to position 2) the control lamp lights up for a short time, then immediately goes out, which confirms that all system components are functioning correctly.
If the warning lamp comes on randomly at any other time, the vehicle owner should seek assistance from a Mercedes-Benz workshop as soon as possible. Such situations include the following:
- a) The control lamp does not turn on when the ignition key is turned to position 2;
- b) The control lamp continues to burn after implementation of start of the engine;
- c) The control lamp is activated and lights up in a constant or flashing mode while the vehicle is moving.
In the presence of the symptoms listed above, the additional security system may fail in a vehicle accident.
Attention! Neglecting the signals of the SRS warning lamp can lead to the most serious consequences if the airbags fail during an accident!
Seat belts with automatic emergency retractors
The tensioners are activated in case of severe frontal overloads that occur in a frontal collision and provide instant removal of the slack in the belts, as a result of which the belts of the latter tightly cover the body of the seated person, significantly increasing the degree of protection for the driver and front passenger.
Seat belt with automatic emergency tensioner
A - tensioner
Tensioner (A) built into the belt return mechanism assemblyThe use of these seat belts is similar to the use of conventional belts equipped with inertial return devices. The tensioner actuation mechanism is absolutely transparent to the user and does not require any additional skills and knowledge from the latter.
The activation of the tensioners occurs only with significant frontal overloads. The operation of the modules is accompanied by a loud bang and a small amount of smoke.
Warning! The smoke emitted during the operation of the tensioners is safe for human health, however, if inhaled directly, it can cause irritation of the mucous membranes.
It should be noted that failures in the operation of tensioners during a frontal collision in most cases are due not to a malfunction of the system, but to the fact that the overloads that occur during an impact do not reach the threshold value at which the modules are activated.
As in the case of airbags, emergency tensioner modules are designed for a single operation and after that they must be replaced complete with belts - contact Mercedes-Benz authorized workshops. All complaints about failures of SRS components are also accepted there.
Maintenance of SRS elements
Airbags and automatic emergency retensioners require little to no regular checks and maintenance. However, the owner of a properly equipped vehicle should keep in mind the following points:
- a) After the airbags have deployed, they must be replaced together with the system control unit. Do not attempt to dismantle used airbags yourself. These operations should be performed only in the conditions of a car service workshop;
- b) If the activation of the SRS warning light indicates a system failure, contact your nearest Mercedes-Benz Dealership without delay for a complete diagnosis and necessary reconditioning of the system. Otherwise, the airbags may not deploy in an accident and fail to perform their protective function;
- c) Only specially trained personnel are allowed to work with the nodes of the additional security system. It is forbidden to dismantle the airbags and emergency seat belt pretensioners from the vehicle. In the event of a SRS failure or after an emergency deployment of the airbags and seat belt tensioners, contact a Mercedes-Benz workshop to have the system components repaired or replaced;
- d) Do not open the modules and do not change the wiring of the airbag systems and automatic emergency tensioner of seat belts - such intervention can lead to involuntary operation of the airbags and tensioners and cause injury to the performer or people nearby;
- e) Do not replace front seats without first consulting a Mercedes-Benz Dealership. Careless or incorrect replacement or removal of the covers may cause the side airbags to fail to deploy in the event of an accident.
When transferring the car to another person, it is mandatory to inform the latter about all installed SRS elements, indicating the relevant paragraphs of the instructions for the rules for using the car.
On all models equipped with SRS, special warning signs are installed at the locations of the active elements of the system.