1997 MERCEDES-BENZ ML320 clock

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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UNDEPLOYED AIR BAG/ETR
After deploying procedures and/or diagnostic testing have confirmed air bag module and/or ETR is
undeployable, contact vehicle manufacturer for proper disposal instructions.
REMOVAL & INSTALLATION
CLOCKSPRING ASSEMBLY
Removal & Installation
1. Before proceeding, see SERVICE PRECAUTIONS . Disable air bag system. See DISABLING &
ACTIVATING AIR BAG SYSTEM .
2. Remove driver air bag module. See DRIVER
-SIDE AIR BAG MODULE . Remove steering wheel bolt.
Using a puller, remove steering wheel. Disconnect lower clockspring connector. Turn 2 fixing screws
(locating on clockspring) counterclockwise until clockspring cannot be rotated. Remove clockspring
mounting screws as necessary. Disconnect all necessary electrical connectors. Remove clockspring
assembly. To install, reverse removal procedure. Activate air bag system. See DISABLING &
ACTIVATING AIR BAG SYSTEM . Perform system operation check to ensure system is functioning
properly. See SYSTEM OPERATION CHECK
.
CONTROL UNIT
Removal & Installation (C Class)
1. Before proceeding, see SERVICE PRECAUTIONS . Disable air bag system. See DISABLING &
ACTIVATING AIR BAG SYSTEM . Remove ignition key. Remove shift lever cover bezel. Lift shift
lever cover enough to disconnect electrical connector. Remove shift lever cover.
2. Remove storage compartment mounting screws from center console. Remove storage compartment.
Remove ashtray. Disconnect electrical connectors as necessary. Disconnect control module electrical
connector. Remove control module mounting bolts. Remove control module.
3. To install, reverse removal procedure. Ensure control module arrow points to front of vehicle. Set
parameters and program new control module with Hand-Held Tester (965 589 00 01 00). 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 gear shift cover panel. Remove
ashtray and ashtray housing at front of console. Remove radio (if necessary).
2. Remove center console right side cover screws and right side cover. Disconnect electrical connector for
control unit. Remove 2 control unit mounting screws. Remove control unit. WARNING:Failure to follow service precautions may result in air bag deployment and
personal injury. See SERVICE PRECAUTIONS
. After component
replacement, check system operation. See SYSTEM OPERATION CHECK
.

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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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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

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77 Instrument cluster
Te ch n ica l
data Instruments
and controlsOperationDrivingInstrument
cluster displayPractical hints Car care Index 1Coolant temperature gauge, see page 81
2Outside temperature indicator (optional), see
page 82
3Fuel gauge with reserve and fuel cap placement
warning lamp, see page 220
4Left turn signal indicator lamp, see exterior lamp
switch, page 90
5Knob for odometer / trip odometer readout / reset,
FSS indicator, and intensity of instrument lamps,
see page 80
64-ETS+ and ESP warning lamp, see page 221
For 4-ETS+ (four wheel electronic traction system),
see page 203;
for ESP (electronic stability program), see page 205.7Speedometer
8Selectable:
Trip odometer, see page 80
Main odometer, see page 80
FSS display, see page 87
Engine oil level indicator, see page 89
9Right turn signal indicator lamp, see exterior lamp
switch, page 90
10Knob for setting clock, see page 80
11Tachometer, see page 82
12Gear range indicator display, see selector lever
positions, page 168
13Clock, see page 80

80 Instrument cluster
Te ch n ica l
data Instruments
and controlsOperationDrivingInstrument
cluster displayPractical hints Car care Index
Activating instrument cluster display
The display for temperature, odometer, oil level
indicator and clock is activated by:
•Opening the driver’s door.
•Pressing button (1) in the instrument cluster (with
key removed or in steering lock position 0).
•Turning the key in steering lock to position 1 or 2.Display illumination
Rotate knob (1) to vary intensity of instrument lamps:
•Clockwise - instrument lamp intensity increases.
•Counterclockwise - instrument lamp intensity
decreases.
Odometer/trip odometer
Activate the instrument cluster.
•Press knob (1) once to switch to or from odometer to
trip odometer readout.
•Press and hold knob (1) for more than 1 second to
reset trip odometer (with trip odometer displayed).
•Press knob (1) twice to display next scheduled
service.
Clock
Adjusting clock (instrument cluster activated):
Minute: Pull out knob (2) and turn it to the right.
Hour: Pull out knob (2) and turn it to the left.

162 Steering lock
Te ch n ica l
data Instruments
and controlsOperationDrivingInstrument
cluster displayPractical hints Car care Index
Steering lock
0The key can be withdrawn in this position only. The
steering is locked when the key is removed from the
steering lock. If necessary, move steering wheel
slightly to allow the locking mechanism to engage.
The key can only be removed with the selector lever
in position “P”. After removing the key or with the
key in steering lock position 0, the selector lever is
locked in position “P”.1Steering is unlocked.
(If necessary, move steering wheel slightly to allow
the key to be turned clockwise to position 1.) Most
electrical consumers can be operated. For detailed
information see respective subjects.
2Driving position.
3Starting position.
See page 164 for starting and turning off the engine.
Wa r n i n g !
When leaving the vehicle always remove the key
from the steering lock, and lock the vehicle. Do not
leave children unattended in the vehicle, or with
access to an unlocked vehicle. Unsupervised use of
vehicle equipment may cause serious personal
injury.

164 Starting and turning off the engine
Te ch n ica l
data Instruments
and controlsOperationDrivingInstrument
cluster displayPractical hints Car care Index
Starting and turning off the engine
Before starting
Ensure that parking brake is engaged and that selector
lever is in position “P” or “N”. Turn key in steering lock
to position 2. The charge indicator lamp should come on.
Starting
Do not depress accelerator.
Briefly turn key in steering lock clockwise to the stop
and release. The starter will engage until the engine is
running.
If engine will not run, and the starting procedure stops,
turn key completely to the left and repeat starting the
engine.
After several unsuccessful attempts, have the system
checked at the nearest authorized Mercedes-Benz Light
Truck Center.
A starting procedure can be interrupted by turning the
key to steering lock position 0.Important!
Due to the installed starter non-repeat feature, the key
must be turned completely to the left before attempting
to start the engine again.
In areas where temperatures frequently drop below -4°F
(-20°C) we recommend that an engine block heater be
installed. Your authorized Mercedes-Benz Light Truck
Center will advise you on this subject.
Note:
In case the engine cannot be started and the
messagesÁ and î are shown in the odometer
display field, the system is not operational. Contact an
authorized Mercedes-Benz Light Truck Center or call
1-800-FOR-MERCedes (in the USA), or 1-800-387-0100
(in Canada).
Turning off
Turn the key in the steering lock to position 0 to stop the
engine.
The key can only be removed with the selector lever in
position “P”.