Mitsubishi Eclipse. Technical Information Manual (1994) — part 84
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
voltage to the SRS diagnostic unit is lost.
Ignition switch
I
I
Multi-purpose
fuse
D C - D C
converter
,
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
between the connector
terminal of the unit and the ground, the squib can be ignited.
(2) The
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
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.
<Driver’s
Air bag module
Supplemental Restraint System (SRS)
1 4 x 0 2 9
Data to be stored
Faults
Fault duration
Number of times
memory can
be erased
Description
All faults stored in
diagnostic codes
The period the warning
light is ON is integrated in
minutes.
(Maximum stored period:
9999 minutes 7 days)
The number of times the
diagnostic codes and fault
durations
have
been
erased by a scan tool is in-
tegrated.
(Maximum number of
times to be stored: 250)
3. Diagnostic function
Fault diagnosis continues to be performed during the period
the ignition switch is ON except during cranking. If a fault
is detected, the SRS warning light is lit.
The microcomputer determines a diagnostic code on the basis
of the results of measurements by various measuring circuits
and stores it in “EEPROM”.
The fault duration (the period the warning light has been ON)
is integrated in increments of a minute and stored in the
PROM together with the diagnostic code. The stored data can
be read and erased by a scan tool. The number of times the
memory has been erased by a scan tool is stored in the
PROM” to provide reference information on the past service
history. The data can be read by a scan tool in the same
way as the fault durations.
NOTE
Once a fault is detected, the SRS warning light continues
to light, even if normal operation of the system is restored,
until the diagnostic code is erased.
4. Automatic diagnostic code erasure function
The automatic diagnostic code erasure function operates
according to the indicated diagnostic code No. (Refer to
Once the malfunction location that causes a diag-
nostic code to be displayed returns to the normal condition,
if the malfunction reoccurs continuously at
inter-
vals, the appropriate malfunction code can be erased. At
this time, if all other diagnostic codes have been erased,
the SRS warning light will switch off and the intermittent
durations of the malfunction will also be erased automatical-
ly. In this case, the erasure is not included in the number
of times erased.
NOTE
If the A/D converter inside the SRS diagnostic unit is mal-
functioning, diagnostic codes No. 41, 42 and 43 will not
be erased by the automatic diagnostic code erasure func-
tion. Furthermore, during cranking, none of the codes will
be erased by this function.
Supplemental Restraint System (SRS)
UNLOCKED
LOCKED
lock lever
Connecter
notch
Lock
Harness side
connector
Primary lock
Forced down
SRS diagnostic
unit side connector
Secondary
lock lever
projection
Lock spring
Primary lock
SRS CONNECTOR
The connector of the SRS diagnostic unit has a double lock
mechanism, fit verification mechanism and connector shorting
mechanism.
DOUBLE LOCK MECHANISM
The mechanism is composed of two mechanisms: each connec-
tor of the SRS diagnostic unit is locked to the connector of
the harness, then these connectors (of the four harnesses)
are locked with the secondary lock lever mounted on the con-
nector of the SRS diagnostic unit side.
The secondary lock lever locking is done as the lock spring
fits in the notch of the connector. The operating principle is
described below.
When Connectors are to be Fitted
(1) The SRS diagnostic unit and harness side connectors are
fitted. (Primary lock)
(2) The secondary lock lever mounted to the SRS diagnostic
unit side connector is pressed down by finger until a click
is heard indicating that the connectors have been locked.
(Secondary lock)
If the harness and SRS diagnostic unit connectors do not
properly fit, the secondary lock lever side projection and
the harness side connector projection interfere with each
other, making it impossible to lock the connectors.
When Connectors are Unlocked
(1) Press in the lock spring with a flat tip
screwdriver to
disengage the lock spring from the notch area of the connec-
tor, and release the lock (secondary lock) of the secondary
lock lever.
Caution
Forced removal of the connector without releasing
the secondary lock lever will result in a damaged lock
lever.
(2) Press the primary lock of each of the harness side connec-
tors and remove the harness side connector.
Supplemental Restraint System (SRS)
Short bar
Secondary
lock lever
side connector
Pressed down
(Press-fitted terminal
Short bar
To body wiring
Press-fitted tab terminals
harness (2-pin)
Short terminal (open)
connector t
Short terminal
connector
FIT VERIFICATION MECHANISM
The mechanism is used to electrically check the engagement
of the connector between the SRS diagnostic unit and the
body wiring harness. The operating principle is described below.
(1) Securely connect the SRS diagnostic unit and harness
side connectors and press the secondary lock lever down
to lock the connectors.
(2) At this time, the short bar provided on the rear surface
of the secondary lock lever produces a short circuit across
terminals No. 7 and 8 of the SRS diagnostic unit. The
SRS diagnostic unit supplies monitoring current to the circuit
to electrically verify that the connectors have been locked.
CONNECTOR SHORTING MECHANISM
The mechanism is designed for prevention of accidental explo-
sion of the inflator when the clock spring connector (for the
squib circuit) is removed from the SRS diagnostic unit. The
operating principle is described below.
When Connectors are Fitted
When the SRS diagnostic unit and clock spring connector are
coupled, the circuit between the short terminals and clock spring
connector terminals are kept in the OFF state by the partition
plate provided in the connector of the SRS diagnostic unit.
When Connectors are Disconnected
When the clock spring connectors are disconnected from the
SRS diagnostic unit, the partition plate between the short termi-
nals and clock spring connector terminals is removed. As a
result, a short circuit is formed between the two poles of the
clock spring connector terminals to prevent generation of a
potential difference (current) between the squib terminals.
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