Safety battery terminal

Depending on the severity of the accident, the safety battery terminal disconnects the starter motor and the alternator from the battery. (only diesel vehicles and R53.)

This minimizes the risk of short circuits in a serious accident. The trigger signal comes from the MRS control unit.

• Airbag warning lamp 

  The airbag warning lamp shows the operational capability of the multiple restraint system (MRS). The airbag indicator lamp in the instrument cluster is activated by the MRS control unit (via the K-bus).

  After the ignition is switched on, the MRS performs a self test. During this time, the airbag indicator lamp will light up (approximately 3 to 5 seconds). When the system is ready for operation, the airbag indicator lamp goes out. If the instrument cluster has not received a bus signal, the airbag indicator lamp will light up.

  If, during the self test or while the vehicle is in motion, the MRS control unit detects an existing fault or one that has been stored, the airbag warning lamp remains on.

  If the MRS detects a fault, the operational capability is partially maintained, subject to the following:

  • If a fault is detected in an MRS circuit, only the affected circuit is deactivated. The other airbags and belt tensioners remain operational.
  • If there is a fault in the airbag warning lamp circuit, the lamp does not light up during the self-test. If there is no other fault, the MRS remains fully operational.

  If there is an internal fault in the MRS control unit or in the power supply, the entire system is deactivated. (airbag and seat belt warning lights come on)

• Seat-belt indicator lamp 

  The seat-belt indicator lamp is the visual seat-belt warning. The visual seat-belt warning instructs the front-seat occupants to fasten their seat belts. Terminal 15 ON activates the visual seat-belt warning.

  The visual seat-belt warning is issued as follows:

  • Seat-belt indicator lamp in the instrument cluster (required by law)
• Indicator lamp for front-passenger airbag deactivation 

  After the ignition is switched on, the MRS performs a self test. In this time, the warning lamp for passenger-airbag deactivation lights up (approx. 3 to 5 seconds). The status of the airbags on the passenger side (passenger airbag and side airbag) is then displayed.

  If the warning lamp for passenger-airbag deactivation ("Passenger Airbag OFF" lamp) is lit, the following airbags on the (occupied) passenger side have been deactivated: front-passenger airbag and side airbag.

  The "Passenger Airbag OFF" lamp is constantly monitored by the MRS control unit. A fault in the power supply or a defective lamp is stored in the MRS control unit's fault memory. If this occurs, the airbag warning lamp is switched on.

  "Passenger Airbag OFF" lamp installation location

  > R50/R53: roof console

  > R52: cowl panel

• Electric fuel pump cutoff 

  Depending on accident severity, the fuel supply may also be cut off.

  Signal path:

  MRS control unit -> K-bus -> General module -> K-bus -> Instrument cluster -> PT-CAN -> DME -> Fuel-pump relay -> Electric fuel pump

  Mechanical components in the multiple restraint system (MRS):

• Belt force limiters on seat belts 

  The seat belts are the primary restraint system for all occupants. Each of the 4 seats is fitted with a lap and diagonal automatic belt.

  To minimize the load on the chest area of the front passengers in the event of a severe head-on collision, the front seat belts are fitted with belt force limiters as standard. The belt force limiters ensure that the belt strap can give slightly if the load exceeds a certain level. The risk of injury due to the belt force acting on the body is thus reduced.

• Knee protection 

An additional impact protection is fitted in the area of the knees on the driver's and front-passenger side. This knee protection provides extensive support for the knees in the event of an accident. The knee protection reduces the load on the lower extremities, especially if the front occupants are not wearing their seat belts.

At the same time, a controlled forward movement of the upper body towards the relevant airbag (driver or passenger airbag) is initiated.