6-24
INTERIOR
-
Supplemental Restraint System (SRS)
2. Supplying squib ignition energy
The energy for ignition of the squib is supplied by two circuits;
the battery of the vehicle and the condensers.
Even if the
Dower
voltage to the SRS diagnostic unit is lost.
d
Ignition switch
<ST>
I
I
Multi-purpose
fuse
yr
DC-DC
converter
L,
vl
L1
()
,
Safing
impact
sensor
the ignition capability is-retained by the condensers for more
than 0.5 seconds.
(1) The two independent battery power supplies (from fuses
4 and 8) are connected via diodes in the diagnostic unit.
If the voltage is larger than
9V
between the connector
terminal of the unit and the ground, the squib can be ignited.
(2) The IGl voltage is boosted to about 25V by the DC-DC
converter to provide more in reserve than the low limit
voltage mentioned above in charging the condensers that
supply the ignition energy.
Caution
1.
When the SRS is to be repaired or parts to be replaced,
make sure that the negative
(-)
cable of the battery
is disconnected beforehand for insulation.
After the negative
(-)
cable of the battery has been
disconnected, wait for more than 60 seconds before
making any service attempt.
The condensers in the SRS diagnostic unit retain for
a given period the voltage necessary for inflating the
air bag even after removal of the battery
voltage.lf
a
service attempt is made during the period, accidental
inflation could cause serious personal injury.
2. Do not measure the resistance across the terminals
of the SRS diagnostic unit. Do not directly touch the
test probe to any of the terminals.
Even if an attempt is made to measure the resistance,
no correct value can be obtained because of the effects
of internal circuits. In addition, there is a danger of
damage to the gold plated portion of the terminals.
<Passen-
<Driver’s
Fron:‘zpact
se::;
igz
side>
\
v
/
Air bag module
19x0592
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