Multiple Restraint System (MRS): Self-test

In addition to all inputs and outputs, the MRS control unit also monitors the internal construction components (self-test). Possible faults are stored in the MRS control unit. In the event of a system error or a fault in a component, the airbag warning lamp lights up.

The MRS control unit starts a self-test after the ignition has been switched on. During this time, the airbag indicator light lights up (approx. 3 to 5 seconds). When the safety system is functional, the airbag warning lamp goes out.

If the instrument cluster does not receive a CAN message from the MRS control unit, the airbag indicator light lights up.

If the MRS control unit has already detected a current or stored fault during the self-test or while the vehicle is being driven, the airbag warning lamp remains switched on.

If a fault is detected in the safety system, the operability of the safety system is partially maintained under the following conditions:

• If a fault is detected in a circuit of the safety system, only the function of the circuit concerned is disabled. The other airbag and seatbelt tensioners remain functional.
• In the event of a fault in the circuit of the airbag warning lamp, the lamp does not light up in the self-test. With the precondition that no other fault is present, the safety system remains functional without restriction.

In the event of an internal malfunction or a fault in the voltage supply in the MRS control unit, the entire safety system is disabled (airbag indicator and seat belt warning lights light up, Check Control message in the instrument panel).