SSANGYONG MUSSO 2003 Service Manual

SECTION 8B
SUPPLEMENTAL RESTRAINT SYSTEM(SRS)
Specifications . . . . . . . . . . . . . . . . . . . . . . . . 8B-1General Specifications . . . . . . . . . . . . . . . . . . 8B-1
Schematic and Routing Diagrams . . . . . . . . 8B-2 Air Bag . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8B-2
Cautions . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8B-3
Function Description . . . . . . . . . . . . . . . . . . 8B-4 Air Bag Module . . . . . . . . . . . . . . . . . . . . . . . . 8B-6
Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . . . . 8B-7 Description . . . . . . . . . . . . . . . . . . . . . . . . . . . 8B-7
Self Diagnosis . . . . . . . . . . . . . . . . . . . . . . . . 8B-10
Circuit Diagram . . . . . . . . . . . . . . . . . . . . . . . 8B-16
TABLE OF CONTENTS
Caution: Disconnect the negative battery cable before removing or installing any electrical unit or when a tool or equipment could easily come in contact with exposed electrical terminals. Disconnecting this cable will help prevent personal injury and damage to the vehicle. The ignition must also be in LOCK unless otherwisenoted.
SPECIFICATIONS
GENERAL SPECIFICATIONS
Application
Air bag System Deployment Time
Detection Time
Operating Temperature
Storage TemperatureAir Bag Replacement Interval
Voltage Range Current Consumption Acceleration Range Max. Acceleration
Voltage Ramp Energy Reservation Inflator Ignition EnergySquib Resistance
Air Bag Warning Lamp ON Time (When Ignition ON) Description
< 20ms< 5ms
-40°C ~ +85°C
-40°C ~ +90°C
Every 10-year after installation 9-16V
5ms after ignition switch ON < 1A,
5ms ~ 5sec. <300mA, after 5sec. < 100mA
+/-50g
+/-600g pulse 0.5 ~ 2.0 V/s
150ms after battery disconnection
4.3mJ
2.15 ± 0.35
6 sec.Air Bag Diagram . . . . . . . . . . . . . . . . . . . . . . 8B-17
Maintenance and Repair . . . . . . . . . . . . . . 8B-18
On-Vehicle Service . . . . . . . . . . . . . . . . . . . . . 8B-18
Air Bag Module . . . . . . . . . . . . . . . . . . . . . . . 8B-18
Clock Spring . . . . . . . . . . . . . . . . . . . . . . . . . 8B-19
Air Bag Control Unit (AC4) . . . . . . . . . . . . . . 8B-21
General Description and System Operation . . . . . . . . . . . . . . . . . . . . . . . . 8B-22
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . 8B-22
Caution . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8B-22

8B-2 SUPPLEMENTAL RESTRAINT SYSTEM(SRS)SCHEMATIC AND ROUTING DIAGRAMS
AIR BAG

SUPPLEMENTAL RESTRAINT SYSTEM(SRS) 8B-3
CAUTIONS
Failure to follow the correct service procedure can cause air bag damage or personal injury due to unexpected air
bag deployment. Before service (removal and installation of part, check for replacement), please be weal noticed offollowing items for your correct service.
1. For service, turn the ignition switch to ‘LOCK’ position and wait for 30 seconds after disconnecting the negative battery cable.
2. If the vehicle collapsed, remove the air bag ECU first to reserve the crash records.
3, Never use other vehicles’ air bag components and replace with specified new part.
4. Never disassemble or repair the air bag module, air bag unit and wiring harness to re-use.
5. Replace the air bag module and air bag unit with new if it dropped, cracked or damaged.
6. Only qualified technicians in service shop should check or repair the air bag,
7. Before service, should be well noticed of warning labels on the vehicle.
A. Sun Visor Side
[Warning] Pull down the sun visor and see SRS air bag warning lamp on the head lining. B. Head Lining
[Warning]
1 . This vehicle is equipped with air bag. Air bag is supplemental device for the seatbelt. Fasten your seatbelt.
2. This air bag should be replaced by authorized supplier within replacement intervals.
3. When the ignition key is turned to ON position, SRS warning lamp will turn on for 6 sec. and go off. In this case, the system is normal. For the following cases, see service manual. - SRS warning lamp does not turn on. - SRS warning lamp does not go off.- SRS warning lamp continues to blink.
C. Steering Wheel Body Inner
[Warning] Before removing the steering wheel, read service manual first. Set the front wheels straight forward
and align the center position marks of SRS clock spring. Improper removal or installation of the steering wheel can damage the SRS components. D. Engine Compartment
[Warning] This vehicle is equipped with air bag. Before checking the engine compartment, read servicemanual first. Faultuy check and service can cause SRS air bag deployment and system defects that can be led to severe damage. E. Battery Cable
[Warning]
Before disconnecting the battery power, read service manual first.

8B-4 SUPPLEMENTAL RESTRAINT SYSTEM(SRS)FUNCTION DESCRIPTION
Air Bag Control Unit (AC4) Air bag control unit (AC4) is installed on the center portion of the front floor tunnel. It is a central control unit that control all functions and determines whether deploy the air bag or not with the collision signal from the built-in accelerometer sensor and has function of diagnosingsystem defects. Internal air bag control unit is consisted as follows;
Microprocessor
ASICs (Upper side ASIC & lower side ASIC)
Accelerometer sensor
Arming sensor
System energy backup condenser
Squib energy backup condenser

SUPPLEMENTAL RESTRAINT SYSTEM(SRS) 8B-5
Input & Output Function Electronic air bag control and diagnosis module is connected by full 30-pin connectors. Input : groundOutput : 1 squib line, warning lampInput/output : communication, diagnosis16 Shorting Bar
17 Shorting Bar
18 Shorting Bar
19 Shorting Bar
20 Diagnosis
21 Shorting Bar
22 Shorting Bar
23 No Pin
24 No Pin
25 Shorting Bar
26 Shorting Bar
2 7 N/A
28 Shorting Bar
29 Shorting Bar
3 0 N/A
1 Lamp
2 Ground
3 N/A
4 N/A
5 Ignition
6 N/A
7 N/A
8 CONF
9 N/A
1 0 N/A 11 N/A
1 2 N/A
13 Squib Line 1(upper)
14 Squib Line 1(lower)
1 5 N/A
IGN
GND
Warning lamp RxD/TxD
Inflator line 1 +
-
5 2 1 20 13
14 Air bag lamp
Communication/ diagnosis
Air bag controlunit
Ground connection or open
Connector Pins
15 30 1
16

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 diagnosisIf 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 switchIf there is fault in the energy reserve system, warning lamp will turn on. And defects are found by continuouschecking 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 ItemsStart-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

8B-10 SUPPLEMENTAL RESTRAINT SYSTEM(SRS)
1. Position the ignition switch to ‘OFF’.
2. Connect the harness connector of scanner to the diagnosissocket in engine compartment.
3. Turn the ignition switch to ‘ON’ position.
4. Select “Electronic control vehicle diagnosis” from function selection display and press ‘Enter’ .
5. Select “Musso (’98 model year)” from vehicle model selection display and press ‘Enter’ .
6. Select “Electronic air bag” from control system selection display and press ‘Enter’ .
7. Select “Self-diagnosis” from diagnosis item selection display.
Notice
Check sensor value of output display, if necessary.
8. Determine the fault code and trace defective component.
NoticeRefer to self-diagnosis list.
SELF DIAGNOSIS