Mercedes-Benz ML320. Service manual - part 1

 

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Mercedes-Benz ML320. Service manual - part 1

 

 

AIR BAG RESTRAINT SYSTEM

1998 AIR BAG RESTRAINT SYSTEMS Mercedes-Benz 

DESCRIPTION & OPERATION 

All models are equipped with Supplemental Restraint System (SRS). The main components of SRS are a driver 
air bag module, passenger air bag module, control unit, SRS warning light, driver knee bolster, passenger knee 
bolster, and Emergency Tensioning Retractor (ETR) seat belt assembly. Additionally, all vehicles provide 
driver-side and passenger-side impact protection by side air bags which are mounted in the driver-side and 
passenger-side doors. Each of the door mounted side air bags utilize sensors which recognize lateral 
acceleration during side impact and signal this to the control module. See Fig. 1 .

NOTE:

Information on ML320 is not available. For WIRING DIAGRAMS, See Fig. 32 .

WARNING:

To avoid injury from accidental air bag deployment, read and carefully 
follow all WARNINGS and SERVICE PRECAUTIONS .

 

1998 Mercedes-Benz ML320 

AIR BAG RESTRAINT SYSTEM 1998 AIR BAG RESTRAINT SYSTEMS Mercedes-Benz

  

 

1998 Mercedes-Benz ML320 

AIR BAG RESTRAINT SYSTEM 1998 AIR BAG RESTRAINT SYSTEMS Mercedes-Benz

  

me 

 

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1998 Mercedes-Benz ML320 

AIR BAG RESTRAINT SYSTEM 1998 AIR BAG RESTRAINT SYSTEMS Mercedes-Benz

  

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Fig. 1: Locating Restraint System Components (E Class Shown; Others Are Similar) 
Courtesy of MERCEDES-BENZ OF NORTH AMERICA 

Both SRS and ETR are electronically activated by a single control unit if a moderately severe to severe frontal 
collision occurs. There are 2 thresholds which must be exceeded to trigger an ETR action, air bag deployment, 
or both. If a moderately severe frontal collision occurs exceeding first triggering threshold where protection 
from safety belt is sufficient, only Emergency Tensioning Retractor (ETR) is activated if safety belt is buckled. 
If a moderately severe frontal collision occurs exceeding first triggering threshold where protection from safety 
belt is sufficient, but safety belt is not buckled, air bag is deployed and EAR is not activated. 

If a severe frontal collision occurs exceeding second triggering threshold where protection from safety belt is 
insufficient, air bag is deployed. EAR is activated if safety belt is buckled. If safety belt is not buckled, ETR is 
not activated when second triggering threshold is reached. Passenger air bag will deploy even if passenger seat 
is not occupied when a triggering threshold is exceeded. If during a severe frontal collision the power supply is 
interrupted, the driver and passenger air bag can still be deployed, but ETR cannot be activated. 

The side air bag on the driver-side deploys whenever the driver-side air bag module is deployed and when there 
is a substantial side impact crash. The air bag on the passenger-side will activate only when a sensor (Occupied 
Seat Recognition Sensor) in the passenger seat sends a signal to the control module that the passenger-side seat 
is occupied. During a collision, the side air bag will then deploy. 

SERVICING 

SRS AIR BAG label on driver-side door latch post indicates SRS replacement date for driver and passenger air 
bag units. All SRS components must be thoroughly inspected, including wiring harness. Before component 
replacement, check for SRS fault codes by performing system operation check. See SYSTEM OPERATION 
CHECK
 . SRS service life is 10 years from manufactured date, or 10 years from SRS replacement date after 
accident related repairs are completed. 

POST-COLLISION INSPECTION 

When a vehicle has been involved in a collision, certain components of the passive restraint system must be 
inspected or replaced. See PASSIVE RESTRAINT SYSTEM INSPECTION article in the GENERAL 
INFORMATION section for post-collision inspection information. 

ADJUSTMENTS 

If fixing screws were not used during clockspring removal or clockspring was rotated during removal, turn 
clockspring clockwise until resistance is detectable. Turn clockspring counterclockwise 2-2.5 turns until fixing 
screws can be unscrewed holding clockspring in this position. 

DISPOSAL PROCEDURES 

WARNING:

An undeployed air bag module or ETR should never be disposed of 
without first being deployed. See SCRAPPED VEHICLE . If deployment is 
not possible, contact vehicle manufacturer for further instructions.

 

1998 Mercedes-Benz ML320 

AIR BAG RESTRAINT SYSTEM 1998 AIR BAG RESTRAINT SYSTEMS Mercedes-Benz

  

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Several situations may arise requiring some form of disposal action, including:

Scrapping a vehicle containing a deployed air bag module and/or ETR.  

Scrapping a vehicle with a live air bag module and/or ETR.  

Disposal of a live but electrically faulty air bag module and/or ETR.  

Disposal of a deployed air bag module and/or ETR.  

DEPLOYED AIR BAG OR ETR 

Deployed air bag module and/or ETR unit can be thrown away. None of its components are reusable. Deployed 
air bag module is NOT classified as hazardous material. 

SCRAPPED VEHICLE 

1. Before proceeding, follow service precautions. See SERVICE PRECAUTIONS . Move vehicle 

outdoors to a remote area, away from workshop and other personnel. Disconnect and shield negative 
battery cable. Open all vehicle windows and doors.  

2. Ensure air bag module is secured to steering wheel, and passenger air bag is secured to dash. Ensure ETR 

seat belt assemblies are secured to "B" pillars and all seat belt buckles are latched. Remove loose objects 
from front seat. DO NOT allow anyone inside vehicle.  

3. Disable air bag system. See DISABLING & ACTIVATING AIR BAG SYSTEM . Connect Trigger 

Device (126-589-00-90-00) and Adapter Cable (126 589 21 63 00) to SRS system connector (X29/9) 
located at passenger footwell area. See Fig. 5 . Move away from vehicle as far as trigger device wiring 
will allow.  

4. To deploy driver air bag and ETR, turn rotary knob on trigger device to position No. 1. Push battery 

check pushbutton and ignition pushbutton simultaneously. Trigger light should illuminate indicating 
driver air bag and ETR deployed. If trigger light is illuminated and driver air bag and/or ETR did not 
deploy, driver air bag module and/or ETR is faulty. See UNDEPLOYED AIR BAG/ETR .  

5. To deploy passenger air bag detonator No. 1, turn rotary knob on trigger device to position No. 2. Push 

battery check pushbutton and ignition pushbutton simultaneously. Trigger light should illuminate 
indicating passenger air bag detonator No. 1 deployed. If trigger light is illuminated and passenger air bag 
detonator No. 1 did not deploy, passenger air bag module is faulty. See UNDEPLOYED AIR 
BAG/ETR
 .  

6. To deploy passenger air bag detonator No. 2, turn rotary knob on trigger device to position No. 3. Push 

battery check pushbutton and ignition pushbutton simultaneously. Trigger light should illuminate 
indicating passenger air bag detonator No. 2 deployed. If trigger light is illuminated and passenger air bag 
detonator No. 2 did not deploy, passenger air bag module is faulty. See UNDEPLOYED AIR 
BAG/ETR
 .  

WARNING:

An undeployed air bag module and/or ETR seat belt CANNOT be disposed 
of without first being deployed. If this is not possible through procedures 
outlined below, contact vehicle manufacturer for further instructions. 
Perform remote deployment outdoors. Keep personnel at least 20 feet 
away.

 

1998 Mercedes-Benz ML320 

AIR BAG RESTRAINT SYSTEM 1998 AIR BAG RESTRAINT SYSTEMS Mercedes-Benz

  

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