eng MERCEDES-BENZ ML500 1997 Complete Repair Manual

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 durin
g 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
.

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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.

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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.

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Removal & Installation
1. Before proceeding, see SERVICE PRECAUTIONS . Disable air bag system. See DISABLING &
ACTIVATING AIR BAG SYSTEM . Remove ignition key. Remove 2 Torx screws from rear of
steering wheel. Lift off air bag module enough to unplug connector from rear of module. Place module
away from work area, with pad facing upward.
2. To install, reverse removal procedure. Tighten Torx screws to specification. See TORQUE
SPECIFICATIONS . Activate air bag system. Perform system operation check to ensure system is
functioning properly. See SYSTEM OPERATION CHECK
.
SIDE AIR BAG UNIT - DRIVER-SIDE & PASSENGER-SIDE
Removal & Installation
1. Before proceeding, see SERVICE PRECAUTIONS . Disable air bag system. See DISABLING &
ACTIVATING AIR BAG SYSTEM . Remove ignition key. Drill out rivets at retaining plate of side air
bag unit. Pull air bag unit out of door. Disconnect connector at driver-side air bag squib. Remove unit
from vehicle. See Fig. 2
.
2. To install, connect connector so that connector audibly clicks when connector engages. Install unit in
door trim panel and rivet using only special rivets (Part No. 003 990 0097). Perform system operation
check to ensure s
ystem is functioning properly. See SYSTEM OPERATION CHECK . which air bag was deployed.

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Fig. 2: Removing Side Air Bag Unit
Courtesy of MERCEDES-BENZ OF NORTH AMERICA
SIDE AIR BAG SENSOR - DRIVER-SIDE & PASSENGER-SIDE
Removal & Installation
1. Before proceeding, see SERVICE PRECAUTIONS . Disable air bag system. See DISABLING &
ACTIVATING AIR BAG SYSTEM . Remove ignition key. On SLK 230, remove door sill moulding.
On all models, remove front seat. Fold floor covering in area toward rear. Unclip connector on side bag
sensor. Remove 2 mounting screws. Remove sensor from vehicle.
2. To install, reverse removal procedure. Ensure that arrow on sensor points toward outside. Perform system
operation check to ensure system is functioning properly. See SYSTEM OPERATION CHECK
.

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Fig. 4: Removing Occupied Seat Recognition Sensor
Courtesy of MERCEDES-BENZ OF NORTH AMERICA
PASSENGER-SIDE AIR BAG MODULE
Removal & Installation (C Class)
1. Before proceeding, see SERVICE PRECAUTIONS . Disable air bag system. See DISABLING &
ACTIVATING AIR BAG SYSTEM. Remove ignition key. Remove instrument panel. Disconnect

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passenger-side air bag module squib connector. Remove 4 passenger-side air bag module mounting nuts.
2. To install, reverse removal procedure. Ensure passenger-side air bag module squib connector audibly
clicks when connecting connector. Activate air bag system. Perform system operation check to ensure
system is functioning properly. See SYSTEM OPERATION CHECK
.
Removal & Installation (E Class)
1. Before proceeding, see SERVICE PRECAUTIONS . Disable air bag system. See DISABLING &
ACTIVATING AIR BAG SYSTEM . Remove ignition key. Remove 2 central mounting bolts for
passenger-side air bag module. Lift air bag module enough to unplug connector from rear of module.
Place module away from work area, with pad facing upward.
2. If necessary to replace passenger air bag installation frame, remove 4 frame mounting bolts. Remove
installation frame from vehicle.
3. To install air bag module or installation frame, reverse removal procedure. Activate air bag system.
Perform system operation check to ensure system is functioning properly. See SYSTEM OPERATION
CHECK .
Removal & Installation (S Class)
1. Before proceeding, see SERVICE PRECAUTIONS . Disable air bag system. See DISABLING &
ACTIVATING AIR BAG SYSTEM . Remove ignition key. Open glove box door. Remove 4 clips
securing glove box. Remove glove box compartment. When removing compartment, disconnect glove
box light. Remove glove box door lock striker.
2. Disconnect passenger-side air bag module squib connector. Remove 4 passenger-side air bag module
mounting nuts. Remove passenger-side air bag module through glove box opening. Place module away
from work area with pad facing up.
3. To install, reverse removal procedure. Ensure module squib connector audibly clicks when connecting
connector. Activate air bag system. Perform system operation check to ensure system is functioning
properly. See SYSTEM OPERATION CHECK
.
Removal & Installation (SL Class)
1. Before proceeding, see SERVICE PRECAUTIONS . Disable air bag system. See DISABLING &
ACTIVATING AIR BAG SYSTEM . Remove ignition key. Remove cover below instrument panel.
Remove one bolt in installation slot of center air outlet, and one bolt below right air outlet.
2. Remove air bag panel (3 Phillips screws and 2 hex bolts). Unplug connector at squib of passenger-side air
bag unit. Remove mounting bolts. Pull off and take air bag out of panel opening.
3. To install air bag module, reverse removal procedure. Activate air bag system. Perform system operation
check to ensure system is functioning properly. See SYSTEM OPERATION CHECK
.
Removal & Installation (CLK 320)
1. Before proceeding, see SERVICE PRECAUTIONS . Disable air bag system. See DISABLING &
ACTIVATING AIR BAG SYSTEM . Remove ignition key. Remove instrument panel. Disconnect
passenger-side air bag module connector. Remove 4 screws and passenger-side air bag module.
2. To install air ba
g module, reverse removal procedure. Activate air bag system. Perform system operation

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check to ensure system is functioning properly. See SYSTEM OPERATION CHECK .
Removal & Installation (SLK 230)
1. Before proceeding, see SERVICE PRECAUTIONS . Disable air bag system. See DISABLING &
ACTIVATING AIR BAG SYSTEM . Remove ignition key. Remove top section of instrument panel.
Fold vapor barrier toward front to reveal 2 screws. Disconnect passenger-side air bag module connector.
Remove 4 screws and passenger-side air bag module.
2. To install air bag module, reverse removal procedure. Activate air bag system. Perform system operation
check to ensure system is functioning properly. See SYSTEM OPERATION CHECK
.
SYSTEM OPERATION CHECK
SRS warning light indicates air bag and Emergency Tensioning Retractor (ETR) system readiness. Turn
ignition on. SRS warning light will light, and then go out after approximately 4 seconds indicating system is
functioning properly. If SRS warning light does not light, lights up while driving or lights all the time, there is a
system fault. Repair malfunctioning system. See DIAGNOSIS & TESTING
.
SERVICE PRECAUTIONS
Observe following precautions when working with air bag systems:
When working around steering column components and before any repairs are performed, disable air bag
system. See DISABLING & ACTIVATING AIR BAG SYSTEM
.
Before straightening any damage to body, or before performing electrical arc-welding, disable air bag
system. See DISABLING & ACTIVATING AIR BAG SYSTEM
.
Always wear safety glasses and gloves when handling a deployed air bag module. Air bag module may
contain sodium hydroxide deposits which are irritating to the skin.
DO NOT repair any portion of SRS wiring harness.
Always handle air bag module with trim cover away from your body. Always place air bag module on
workbench with trim cover up, away from loose objects.
DO NOT expose any SRS component to temperatures in excess of 212°F (100°C).
DO NOT expose any SRS component to cleaning agents such as solvents, gasoline, lye, etc.
DO NOT connect Hand-Held Tester (6511 0001 99) to Data Link Connector (DLC) with ignition on.
Damage to HHT may result.
DO NOT connect HHT (6511 0001 99) to vehicle if a battery charger is connected to vehicle battery.
Damage to HHT may result.
DISABLING & ACTIVATING AIR BAG SYSTEM DISABLING SYSTEM
Before proceeding, follow air bag service precautions. See SERVICE PRECAUTIONS
. Turn ignition off.
Disconnect and shield negative battery cable. Remove passenger foot mat. Remove passenger footrest.
Disconnect SRS system connector (X29/9) located at passenger footwell area. See Fig. 5
. System is now
disabled.

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If any part of SRS wiring harness is damaged, DO NOT repair wiring harness, replace complete wiring harness.
TORQUE SPECIFICATIONS
TORQUE SPECIFICATIONS
(1)
DIAGNOSIS & TESTING
Before proceeding, see SERVICE PRECAUTIONS
. The control module is capable of diagnosing airbag
system components and ETR components. If a fault is detected by the control module or system is
malfunctioning, SRS warning light will do one or more of the following:
SRS warning light goes out after 2 minutes. System fault is noted, however occupant protection is not
affected. See RETRIEVING FAULT CODES
.
SRS warning light illuminates continuously. System is faulty which may result in a non deployment or
false deployment. See RETRIEVING FAULT CODES
.
SRS warning light blinks continuously. Control module has been replaced without setting control module
parameters.
RETRIEVING FAULT CODES
1. Check vehicle fuses. Replace any blown fuses as necessary. Ensure vehicle battery voltage is 11 volts or
more. Ensure SRS warning light functions. Turn ignition off. Connect Hand-Held Tester (HHT) (965 589
00 01) to Data Link Connector (DLC).
2. DLC is located in right rear corner of engine compartment. It may be necessary to use Adapter (965 589
00 40 or 965 589 00 50) to connect HHT to DLC. After HHT displays module number and version, press
return key to start diagnosis. Using HHT, follow HHT prompts to retrieve SRS fault codes.
3. HHT will display a 3 digit fault code, and may display additional graphic information. This additional
graphic information will help in diagnosis of fault code. See Fig. 6
. During diagnosis HHT will display 4
different graphic displays informing technician if a test passes or fails, or if seat belt buckle is latched or
not latched. See Fig. 6
.
4. These
graphic displays are displayed as applicable by HHT during testing. See FAULT CODES table.
ApplicationFt. Lbs. (N.m)
Steering Wheel Hub Bolt52-66 (70-90)
INCH Lbs. (N.m)
Driver Air Bag Module Bolts (Torx)44-62 (5-7)
(1)Torque specifications are not available for clockspring assembly, control module or passenger-side
air bag module.
NOTE: After component replacement, perform a system operation check to ensure
proper system operation. See SYSTEM OPERATION CHECK
.
NOTE: Fault codes may only be retrieved using Hand-Held Tester (965 589 00 01) and
Adapter (965 589 00 40 or 965 589 00 50).

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FAULT CODES
Code (Possible Cause)
Go To Test Step (See
Fig.)
00
(SRS Control Module, N2/2)2.0
003
(Voltage Supply Circuit 15R, Low Voltage)1.0
002
(SRS Warning Light, A1e15)11.0
004
(Driver Air Bag Squib, R12/3)3.0, 4.0 (7, 9)
005
(Driver ETR Squib, R12/1)5.0
006
(Passenger ETR Squib, R12/2)7.0
007
(Passenger Air Bag Squib, R12/4)9.0, 10.0 (12, 13)
008
(Side Air Bag Squib, Driver-Side)17.0
009
(Side Air Bag Squib, Passenger- Side)18.0
016
(Driver Belt Switch, S68/3)12.0, 13.0
017
(Passenger Belt Switch, S68/3)14.0, 15.0
018
(Driver Air Bag Harness)19.0
019
(Driver Air Bag Sensor)Replace Sensor
020
(Driver Air Bag Sensor)Replace Sensor
021
(Passenger Air Bag Sensor)20.0
022
(Passenger Air Bag Sensor)Replace Sensor
023
(Passenger Air Bag Sensor)Replace Sensor
024
(Passenger Seat Occupation Signal)21, 22 (21, 22)
025
(Passenger Seat Occupation Signal)21

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