1997 MERCEDES-BENZ ML350 sensor

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
.

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
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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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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
.

1998 Mercedes-Benz ML320
AIR BAG RESTRAINT SYSTEM 1998 AIR BAG RESTRAINT SYSTEMS Mercedes-Benz
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Fig. 3: Removing Side Air Bag Sensor (E Class Shown; Others Are Similar)
Courtesy of MERCEDES-BENZ OF NORTH AMERICA
OCCUPIED SEAT RECOGNITION SENSOR
Removal & Installation
1. Before proceeding, see SERVICE PRECAUTIONS . Disable air bag system. See DISABLING &
ACTIVATING AIR BAG SYSTEM .
2. Remove cover on front seat cushion. Remove ignition key. Unclip connection for occupied seat
recognition sensor on seat connector block. Remove electrical connection lead from seat and pull upward
out of rubberized fiber matting. See Fig. 4
.
3. To install, lay out occupied seat recognition sensor uniformly on rubberized fiber matting. Fabric side
should point upward. Do not kink occupied seat sensor. Reverse removal procedure. Perform system
operation check to ensure s
ystem is functioning properly. See SYSTEM OPERATION CHECK.

1998 Mercedes-Benz ML320
AIR BAG RESTRAINT SYSTEM 1998 AIR BAG RESTRAINT SYSTEMS Mercedes-Benz
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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

1998 Mercedes-Benz ML320
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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

1998 Mercedes-Benz ML320
AIR BAG RESTRAINT SYSTEM 1998 AIR BAG RESTRAINT SYSTEMS Mercedes-Benz
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with HHT connected to DLC and ignition key removed. Remove driver-side air bag module. Disconnect
driver-side air bag module squib connector R12/3. Connect Resistance Substitution Unit (124 589 09 63)
to driver-side air bag module squib connector (harness side). Set resistance substitution unit to 2 ohms.
Turn ignition key to position "2". Read NOMINAL VALUE/HHT DISPLAY column. If HHT displays a
check, replace driver-side air bag module. If HHT displays an "F", go to step 3.2.
Read TEST CONNECTION (NOT FOR HHT) column. Horn/air bag clockspring connector A45x1,
terminals No. 1 and 2 are identified. Read TEST CONDITION column. Test circuit with HHT connected
to DLC. Remove ignition key. Connect Resistance Substitution Unit (124 589 09 63 00) to horn/air bag
clockspring connector A45x1. Set resistance substitution unit to 2 ohms. Read NOMINAL VALUE/HHT
DISPLAY column. If HHT displays a check, check horn/air bag clockspring for continuity. Replace
horn/air bag clockspring as necessary. If HHT displays an "F", go to step 3.4.
MODEL IDENTIFICATION
COMPONENT IDENTIFICATION
DIAGNOSTIC TESTS NOTE: Some testing is identified by model number. To identify models by model
number see MODEL IDENTIFICATION
table.
Model NumberModel
129SL Class
140S Class
170SLK 230
202C Class
208CLK 320
210E Class
ComponentManufacturer's Designation
A45Horn/Air Bag Clockspring
A53Driver-Side Air Bag Sensor
A54Passenger-Side Air Bag Sensor
B41/1Passenger-Side Seat Occupied Recognition Sensor
N2/2Control Module
R12/1Driver-Side ETR Squib Connector
R12/2Passenger-Side ETR Squib Connector
R12/3Driver-Side Air Bag Squib Connector
R12/8Passenger-Side Air Bag Squib Connector
R12/9Side Air Bag (Driver-Side)Squib Connector
R12/10Side Air Bag (Passenger-Side) Squib Connector
S68/3Driver-Side Belt Buckle Switch
S68/4Passenger-Side Belt Buckle Switch
W26Control Module Ground
X11/4Data Link Connector

1998 Mercedes-Benz ML320
AIR BAG RESTRAINT SYSTEM 1998 AIR BAG RESTRAINT SYSTEMS Mercedes-Benz
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Fig. 28: Testing Side Air Bag Sensor
Courtesy of MERCEDES-BENZ OF NORTH AMERICA

1998 Mercedes-Benz ML320
AIR BAG RESTRAINT SYSTEM 1998 AIR BAG RESTRAINT SYSTEMS Mercedes-Benz
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