Safety Restraint System

How does the airbag work?

The physics behind airbags is pretty
simple: on-board sensors look out for
movements that indicate a vehicle
has been involved in a collision,
triggering the airbag to fire if a crash
is detected.

How is it set off?

When this happens, a small explosive
device detonates within an airbag
module, inflating the bag, which fills
with Chemical gas to protect vehicle
occupants.

The technology has developed over
the years, with some airbags able to
detect the forces involved in a
collision, inflating to the correct
amount based on this data.

SRS relation

Airbags are also known as
‘supplementary restraint or Safety
Restraint devices’ because they are
designed to work in conjunction with
seatbelts, which themselves control
how your body behaves in a crash.
This name is what some airbags are
labelled as ‘SRS’.

How to check system

First logical step is to scan the
vehicle for any codes relating to the
SRS. Document, research, check for
safety recalls or TSB’s. Then proceed
with monitoring scan data to
determine exact component not
communicating with the SRS module.

(The srs module is ohm’ing components when

key is on. There is no reason to ohm and airbag
with a DVOM, ever).

Further diagnostic

Check for blown fuses in the circuit to confirm or
deny a component pulling to many amps due to
internal short. Always check connectors
underneath the seat for obstruction or
disconnection due to passengers. Verify all seat
belts go in and out of latches with ease. Find
manufacturers specifications for resistance on
each components. Then after verifying good
connections and fuse proceed with determining
which component failed by following step by
step test procedures released by manufacture.

Tying in SRS

The primary component of the SRS is
the airbag, which is typically located
in the steering wheel for the driver
and in the dashboard or side panels
for the front passenger. However,
understanding other sensors involved
will allow for better understanding of
full communication.

Impact sensor

These sensors respond to several
different sets of stimuli, including
sudden stopping, increased pressure
as pieces of the car are moved due to
the force of the collision, and more.
Impact sensors that measure the
direction and intensity of an impact in
the front, rear and sides of the
vehicle.

Clock spring

Clocksprings generally consist of a flat
multicore cable wound in a spiral shape similar
to a clock spring, hence the name. The part gets
its name as it resembles the spiral wound main
spring of a clock however its function is to be a
flexible electrical connector; not to be a spring to
store energy. Note; for many years there was
only the horn that required a single
wire/conductor from the steering wheel to the
stationary parts of the car. that connection was
made either by allowing the wire to twist /
untwist as the steering wheel turned or possibly
a commutator and brush arrangement would be
used.