Mercedes-Benz 350 SDL Owner's Manual page 41

Driver Airbag
The most effective occupant restraint
system yet developed for use in
production vehicles is the three-point
seat belt. In some cases, however,
the protective effect of seat belts can
be further enhanced by an airbag.
The airbag (1) is located in the
steering wheel hub and, in conjunction
with wearing the seat belts with
emergency tensioning retractors (2),
provides increased protection for the
driver.
The operational readiness of the
airbag system is verified by the
indicator lamp "SRS" (3) in the
instrument cluster. If no fault is
detected, the lamp will go out after
approximately 4 seconds; after the
lamp goes out, the system continues
to monitor the components and
circuitry of the airbag system and will
indicate a malfunction by coming on
again.
The following system components are
monitored or undergo a self-check:
crash-sensor, airbag ignition circuit,
driver and front passenger seat belt
buckles. Initially, when the key is
turned from steering lock position 0 to
positions 1 or 2, malfunctions in the
crash-sensor are detected and
indicated (the "SRS" indicator lamp
stays on longer than 4 seconds).
In the operational mode, after the
indicator lamp has gone out after the
initial check, interruptions and short
circuits in the airbag ignition circuit
and in the driver and front passenger
seat belt buckle harnesses, and low
voltage in the entire system are
detected and indicated.