SsangYong Musso. Manual - part 544

8B-6 SUPPLEMENTAL RESTRAINT SYSTEM(SRS)

AIR BAG MODULE

Air bag module is installed in the pad of steering wheel center and inflator is consisted of igniter, explosives, gas
generating material and bag. When crashed, the air bag control unit sends current to the air bag module through
squib line and this current ignites as ignition energy (6mJ) momentarily igniting explosives and bag will be inflated
by nitrogen gas protecting driver at the same and then deflates.

1 Air bag Module
2 Module Housing
3 Bag
4 Module Bracket

5 Retainer Ring
6 Inflator
7 Horn Switch
8 Backing Plate

SUPPLEMENTAL RESTRAINT SYSTEM(SRS) 8B-7

DIAGNOSIS

DESCRIPTION

Air bag control unit continuously controls system function as follows during ignition ON or driving.

Recognition of collision

Internal diagnosis

External diagnosis

If recognize or detect defects, warning lamp will turn on. If there is danger of improper deployment, the system will
enter overall shutdown status and the air bag will not inflate.

Air bag control unit will store detected internal and external defects in the EEPROM.

System Control

Battery Voltage Check

Battery voltage will be monitored continuously. If voltage is out of normal operating range, all system diagnosis will
stop and warning lamp turn on.

Battery Voltage (V)

< 8.7

9 - 16

> 16.3

Function

System diagnosis stops and warning lamp turns on

Normal operation range

System diagnosis stops and warning lamp turns on

Squib Diagnosis

It checks not only high (4.50.5) or low (1.40.5) resistance but also short resistance (1- 10k) status between the
battery and ground to indicate defects in squib line by blinking warning lamp. Air bag control unit (AC4) can measure
squib resistance.

Warning Lamp Turning On

Air bag control unit detects system defects during ignition ON or driving and displays following 2 warning lamps.

Warning lamp ON: internal defects of the air bag control unit

Warning lamp blinking: higher resistance than standard in the squib line or short at the battery or ground,

Safety Function Check

It checks defects during operation of the arming sensor If the sensor is shorted for more than 2 seconds, the module
will enter overall shutdown mode.

Temperature Sensor

Function of the temperature sensor will be monitored continuously. If there is fault due to defective sensor or short,
the lamp will turn on and program will take calibration temperature (25) of collision conditions.

Power Supply

Airbag control unit operates in 9-16v and the characteristic of the system has backup condenser to supply the power
for max.150ms if there is power defect during collision.

8B-8 SUPPLEMENTAL RESTRAINT SYSTEM(SRS)

Energy Reserve System

Energy reserve system is consisted of condensor and energy switch and will check following items continuously
during system operation.

High voltage

Low voltage

Low rating capacity

Function of the energy reserve switch

If there is fault in the energy reserve system, warning lamp will turn on. And defects are found by continuous

checking of the condenser voltage, the system will enter overall shutdown status for safety reason.

Shutdown Switch

There is 1 energy shutdown switch in the system and it will be checked during start-up. And it also checks that
condenser is discharging properly. If shutdown switch is short, it will be detected during condensor voltage test.

If squib line fault is obvious, the warning lamp will turn on and the module will enter overall shutdown status.

Accelerometer Check

Accelerometer function will be checked during start-up. During operation, accelerometer off-set signal will be checked,
If there is fault, module will enter overall shutdown status.

ASIC Overheat

Module monitors upper side ASIC overheats continuously. If overheated, the module will enter overall shutdown
status.

Microprocessor Fault

Module checks EEPROM, ROM checksum and RAM during start-up. EEPROM tests checksum operation.

If RAM or ROM checksum is defective, module will not allow start-up continuously but will be re-set,

If EEPROM is defective, warning lamp will turn on and the module will enter overall shutdown status.

During operation, RAM will continuously verify the proper operation of temporary memory program data usage. If
there is fault, the module will enter overall shutdown status and the warning lamp will turn on.

Watchdog Test

Watchdog function will be tested in start-up. If there is fault during the test, warning lamp will turn on and the module
will enter overall shutdown status.

SUPPLEMENTAL RESTRAINT SYSTEM(SRS) 8B-9

Diagnosis

Air bag control unit diagnoses each function in the intervals of 250ms - 20 sec. during start-up or driving to prevent
unwanted air bag deployment. If there is defect, it turns on or blinks warning lamp to indicate defects in the air bag
system to the driver. And fatal defect is found, air bag control unit enters overall or partial shutdown status and fault
code will be stored.

Air bag control unit diagnoses following items.

- Ignition TR

- Acceleration

- Microprocessor, RAM and ROM

- Watchdog

- Shutdown Switch

Diagnosis Condition

Diagnosis Items

Start-up (ignition ON)

During Driving

Lamp Blinking Mode

There are 2 kinds of blinking mode

1. When system internal fault is found, the lamp will stay on.

2. The lamp will blink according to external fault and there are 2 blinking codes.

Blinking code 1 (Squib resistance fault in the driver’s air bag squib line)

Blinking code 2 (Squib short on plus and minus in the air bag squib line)

Lamp blinking code is as follows. The last blinking will be within 0.5 sec. and 1 cycle of blinking will be repeated every
5 seconds.

Blinking Code 1

(Sec.) 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

Blinking Code 3

(Sec.) 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5

- Squib resistance

- Squib line short to battery and ground

- Energy reserve system

- Lamp output

- Battery voltage

- ASIC communication

- Arming sensor

- ASIC overheating

- RAM and W/D

- EEPROM

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