Mitsubishi Galant (2004+). Manual - part 1735

CONSTRUCTION AND OPERATION

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-13

FRONT IMPACT SENSOR

M2521005000099

CAUTION

Improper services cause the sudden operation of 
SRS (air bag) or the system to be inoperative. Do 
not disassemble or tamper with the front impact 
sensor to prevent the serious injury.
The front impact sensors are installed on both radia-
tor support panels.

The front impact sensors transmit acceleration data 
to SRS-ECU. The SRS-ECU then determines 
whether to operate the driver’s air bag, front passen-
ger’s air bag and seat belt pretensioners, and then 
outputs an ignition signal when necessary. The front 
impact sensor also diagnoses itself, and sends a 
diagnosis code to the SRS-ECU if a problem occurs. 

SIDE IMPACT SENSOR

M2521006000081

CAUTION

Improper services cause the sudden operation of 
SRS (air bag) or the system to be inoperative. Do 
not disassemble or tamper with the side impact 
sensor to prevent the serious injury.
The side impact sensors are installed in the lower 
part of the center pillar.

The side impact sensors transmit acceleration data 
to the SRS-ECU. The SRS-ECU then determines if 
the side air bags should be inflated, and sends an 
ignition signal. The side impact sensor also diag-
noses itself, and sends a diagnosis code to the 
SRS-ECU if a problem occurs. 

AC306681

AC306331

AC308439

AB

HEAD LIGHT
(RH)

FRONT IMPACT SENSOR

AC308953AB

SIDE IMPACT
SENSOR

CENTER PILLAR

CONSTRUCTION AND OPERATION

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-14

SEAT SLIDE SENSOR

M2521001400017

CAUTION

Improper services cause the system to be inop-
erative.  Do not disassemble or tamper with the 
seat slide sensor to prevent the serious injury.
The seat slide sensor is attached to the seat rail and 
provides the air bag control unit with information on 
the seat position.

The air bag control unit controls deployment output 
of the driver’s air bag in accordance with the informa-
tion from the sensor.

OCCUPANT CLASSIFICATION SENSOR

M2521001300010

AC306933

AC306617

AC306418

AB

SEAT SLIDE SENSOR

SEAT SLIDE
SENSOR

SHIELD PLATE

AC308898

OCCUPANT 
CLASSIFICATION-ECU

OCCUPANT 
CLASSIFICATION
SENSOR

AB

CONSTRUCTION AND OPERATION

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-15

CAUTION

Improper services cause the system to be inop-
erative.  Do not disassemble or tamper with the 
occupant classification sensor to prevent the 
serious injury.
The occupant classification sensors are attached to 
the seat rails and provide the air bag control unit with 
information on the weight applied to the front passen-
ger seat.

The air bag control unit controls deployment output 
of the front passenger’s air bag in accordance with 
the information from the sensor. The front passen-
ger’s air bag does not deploy in an impact when the 
weight applied to the seat is sensed as less than 66 
pounds (30 kg).

SEAT BELT WITH PRE-TENSIONER

M2521008000128

CAUTION

Improper services cause the sudden operation of 
the seat belt with pre-tensioner or the system to 
be inoperative.  Do not disassemble or tamper 
with the seat belt to prevent the serious injury.
The seatbelt incorporating the pretensioner automat-
ically winds the seatbelt upon front impact to reduce 
forward shifting of the driver’s and passenger’s.
The seat belt pre-tensioner is built into the driver's 
and passenger's front seat belt retractor. 

Upon front impact, the seat belt pre-tensioner ignites 
the gas generator and emits gas with the SRS-ECU 
signal when the front impact sensor and the 
SRS-ECU detects a gravitational impact at the same 
time. The gas pressure shifts the ball in the pipe and 
the balls comes in contact with the protrusion of the 
ring gear, is inserted in the ring gear. The ring gear 
rotates to wind the webbing.
When the seatbelt switch indicates that the seatbelt 
is not worn, the pretensioners are deactivated by 
SRS-ECU. 

AC309018AB

RING GEAR

PIPE

BALL

GAS GENERATOR

CONSTRUCTION AND OPERATION

SUPPLEMENTAL RESTRAINT SYSTEM (SRS)

52B-16

PASSENGER SEAT BELT WARNING LIGHT

M2521001500014

The light normally comes on when the ignition switch is turned 
to the "ON" position and goes off a few seconds later.
The light comes on when a person sits on the front passenger 
seat but does not fasten the seat belt.

PASSENGER AIR BAG OFF INDICATOR LIGHT

M2521001600011

The indicator normally comes on when the ignition switch is 
turned to the "ON" position and goes off a few seconds later.
In the following situations, the indicator will stay on to show that 
the front passenger air bag is not operational.

•

The occupant classification sensors sense 66 pounds (30 
kg) on the front passenger seat.

•

The front passenger’s seat is not occupied.

When the weight applied to the front passenger seat is sensed 
as 66 pounds (30 kg) or greater, the indicator goes off to show 
that the passenger front air bag is operational.

SRS-ECU

M2521007000170

CAUTION

Improper services cause the sudden operation of 
SRS (air bag) or the system to be inoperative. Do 
not disassemble or tamper with the SRS-ECU to 
prevent the serious injury.
The SRS-ECU incorporates a front analog G-sensor 
and front safing G-sensor for frontal collisions and a 
side-airbag safing G-sensor for side collisions. Upon 
front impact, the SRS-ECU set the ignition signal to 
the driver’s air bag module, the front passenger’s air 
bag module and the seat belt pre-tensioner when the 
front impact sensor and the SRS-ECU detects a 
gravitational impact at the same time. Upon side 
impact, the SRS-ECU set the ignition signal to the 
side air bag module suffered a impact, when the side 
impact sensor and the SRS-ECU detects a gravita-
tional impact at the same time.

The SRS-ECU is provided with the following capabil-
ities:

•

Backup power supply in case of power failure in 
collisions

•

Self-diagnosis function to avoid system’s opera-
tion errors and to improve its reliability

DIAGNOSTIC FUNCTION

The SRS-ECU has the following functions to make 
system checking easily using the scan tool.

•

Diagnostic trouble code output

•

Service data output

•

Actuator test

•

Accuracy check occupant classification sensor 

CAN COMMUNICATION

SRS-ECU, through CAN communication, outputs a 
signal that requests SRS warning lamp illumination 
to the meter ECU.

AC306329AC

PASSENGER'S 
SEAT BELT
WARNING 
LIGHT

AC306329AB

PASSENGER'S 
AIR BAG OFF
INDICATOR 
LIGHT