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

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

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

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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