brake MERCEDES-BENZ GLK-Class 2014 X204 Owner's Manual

ATTENTION ASSIST
Activating/deactivating .................229
Display message ............................ 251
Function/notes ............................. 201
Audio menu (on-board
computer) .......................................... 226
Audio system see separate operating instructions
Authorized Centers
see Qualified specialist workshop
Authorized Mercedes-Benz Center
see Qualified specialist workshop
Authorized workshops
see Qualified specialist workshop
AUTO lights
Display message ............................ 246
see Lights
Automatic engine start (ECO start/
stop function) .................................... 149
Automatic engine switch-off (ECO
start/stop function) ..........................149
Automatic headlamp mode ..............113
Automatic transmission Automatic drive program ...............156
Changing gea r............................... 155
DIRECT SELECT lever .....................152
Display message ............................ 258
Driving tips .................................... 155
Emergency running mode ..............158
Engaging drive position .................. 154
Engaging neutral ............................ 153
Engaging park position
automatically ................................. 153
Engaging reverse gear ...................153
Engaging the park position ............153
Kickdown ....................................... 155
Manual drive program ....................156
Overview ........................................ 152
Problem (malfunction) ...................158
Program selector button ................155
Pulling away ................................... 147
Starting the engine ........................147
Steering wheel paddle shifters ......156
Trailer towing ................................. 155
Transmission position displa y........ 153
Transmission positions ..................154
Automatic transmission
emergency mode ............................... 158 B
Backup lamp Changing bulbs .............................. 122
Display message ............................ 245
Bag hook ............................................ 278
Ball coupling Installing ........................................ 214
Removing ....................................... 216
Storing ........................................... 217
BAS (Brake Assist System) .................68
BAS PLUS (Brake Assist System
PLUS) .................................................... 68
Battery (SmartKey) Checking .......................................... 79
Important safety notes ....................78
Replacing ......................................... 79
Battery (vehicle)
Charging ........................................ 318
Display message ............................ 249
Important safety notes ..................316
Jump starting ................................. 320
Blind Spot Assist
Activating/deactivating .................229
Display message ............................ 253
Notes/function .............................. 202
Trailer towing ................................. 204
see Active Blind Spot Assist
BlueTEC
Adding DEF .................................... 162
BlueTEC (DEF) .................................... 370
Brake Assist see BAS (Brake Assist System)
Brake fluid
Display message ............................ 238
Notes ............................................. 372
Brake lamps
Display message ............................ 244
Brakes
ABS .................................................. 67
BAS .................................................. 68
BAS PLUS ........................................ 68
Brake fluid (notes) .........................372
Display message ............................ 236
Driving tips .................................... 168
Important safety notes ..................168
Maintenance .................................. 169 Index
5

Parking brake
........................ 165, 169
Warning lamp ................................. 263
Breakdown
see Flat tire
see Towing away/tow-starting
Bulbs
see Replacing bulbs C
California Important notice for retail
customers and lessees ....................24
Calling up a malfunction
see Display messages
Car
see Vehicle
Care
Carpets .......................................... 312
Car wash ........................................ 306
Display ........................................... 310
Exterior lights ................................ 309
Gear or selector lever ....................311
Interior ........................................... 310
Matte finish ................................... 308
Notes ............................................. 305
Paint .............................................. 307
Plastic trim .................................... 310
Power washer ................................ 307
Rear view camera .......................... 309
Roof lining ...................................... 312
Seat belt ........................................ 312
Seat cover ..................................... 311
Sensors ......................................... 309
Steering wheel ............................... 311
Tail pipes ....................................... 310
Trim pieces .................................... 311
Washing by hand ........................... 306
Wheels ........................................... 307
Windows ........................................ 308
Wiper blades .................................. 308
Wooden trim .................................. 311
Cargo compartment cover ...............278
Cargo compartment
enlargement ...................................... 276
Cargo compartment floor Opening/closing ............................ 281
Stowage well (under) .....................281Cargo net
Attaching ....................................... 280
Important safety information .........279
Cargo tie down rings .........................277
Car wash (care) ................................. 306
CD player/CD changer (on-board
computer) .......................................... 226
Center console Lower section .................................. 37
Upper section .................................. 36
Central locking
Automatic locking (on-board
computer) ...................................... 232
Locking/unlocking (SmartKey) ........76
Changing bulbs
Cornering light function .................121
High-beam headlamps ...................120
Low-beam headlamps ....................120
Parking lamps ................................ 120
Reversing lamps ............................ 122
Standing lamps (front) ...................120
Turn signals (front) ......................... 121
Child-proof locks
Important safety notes ....................66
Rear doors ....................................... 66
Children
In the vehicle ................................... 61
Restraint systems ............................ 61
Special seat belt retractor ...............64
Child seat
LATCH-type (ISOFIX) child seat
anchors ............................................ 64
Top Tether ....................................... 65
Cigarette lighter ................................ 284
Cleaning Mirror turn signal ........................... 309
Trailer tow hitch ............................. 310
Climate control
Adjusting the airflow (AIR FLOW) ...135
Automatic climate control (3-zone) 132
Controlling automatically ...............135
Cooling with air dehumidification ..133
Defrosting the windows .................138
Defrosting the windshield ..............137
Dual-zone automatic climate
control ........................................... 129
Important safety notes ..................128
Indicator lamp ................................ 135 6
Index

Delayed switch-off
Exterior lighting (on-board
computer) ...................................... 231
Interior lighting .............................. 232
Diagnostics connection ......................26
Diesel ................................................. .370
Digital speedometer .........................224
DIRECT SELECT lever see Automatic transmission
Display (cleaning instructions) ........310
Display messages ASSYST PLUS ................................ 300
Calling up (on-board computer) .....235
Driving systems ............................. 251
Engine ............................................ 247
General notes ................................ 235
Hiding (on-board computer) ...........235
KEYLESS-GO .................................. 260
Lights ............................................ .243
Safety systems .............................. 236
SmartKey ....................................... 260
Tires ............................................... 256
Vehicle .......................................... .258
Distance recorder ............................. 223
see Odometer
see Trip odometer
Distance warning (warning lamp) ....271
DISTRONIC PLUS Activation conditions .....................177
Deactivating ................................... 181
Display message ............................ 254
Displays in the multifunction
displa y........................................... 180
Driving tips .................................... 182
Function/notes ............................. 175
Important safety notes ..................175
Setting the specified minimum
distance ......................................... 180
Warning lamp ................................. 271
Doors
Automatic locking (on-board
computer) ...................................... 232
Automatic locking (switch) .............. .82
Central locking/unlocking
(SmartKey) ...................................... .76
Control panel ................................... 39
Display message ............................ 259
Emergency locking ........................... 83 Emergency unlocking
.......................83
Important safety notes ....................81
Opening (from inside) ......................81
Drinking and driving .........................166
Drinks holder see Cup holder
Drive program
Automatic ...................................... 156
Display ........................................... 153
Display (DIRECT SELECT lever) ......153
Manual .......................................... .156
Driver's door
see Doors
Driving abroad
Mercedes-Benz Service .................301
Symmetrical low bea m.................. 112
Driving in mountainous terrain
Approach/departure angl e............ 173
Driving lamps
see Daytime running lamps
Driving off-road
see Off-road driving
Driving safety systems
ABS (Anti-lock Braking System) .......67
BAS (Brake Assist System) ..............68
BAS PLUS (Brake Assist System
PLUS) .............................................. .68
Electronic brake force distributio n... 72
ESP ®
(Electronic Stability
Program) .................................... 69, 70
ETS/4ETS (Electronic Traction
System) ........................................... 70
Important safety information ...........67
Overview .......................................... 67
PRE-SAFE ®
Brake ............................ .72
Driving systems
360°camera .................................. 197
Active Blind Spot Assist .................206
Active Driving Assistance package 206
Active Lane Keeping Assist ............209
Active Parking Assist .....................188
ATTENTION ASSIST ........................201
Blind Spot Assist ............................ 202
Cruise control ................................ 173
Display message ............................ 251
DISTRONIC PLUS ........................... 175
HOLD function ............................... 1838
Index

Lane Keeping Assist
......................204
Lane Tracking package ..................202
PARKTRONIC ................................. 185
Rear view camera .......................... 192
Driving tips
Automatic transmission .................155
Brakes ........................................... 168
Break-in period .............................. 144
DISTRONIC PLUS ........................... 182
Downhill gradient ........................... 168
Drinking and driving .......................166
Driving abroad ............................... 112
Driving in winter ............................ .170
Driving on flooded roads ................170
Driving on sand .............................. 172
Driving on wet roads ......................170
Driving over obstacles ...................172
Exhaust check ............................... 166
Fuel ................................................ 166
General .......................................... 166
Hydroplaning ................................. 170
Icy road surfaces ........................... 171
Limited braking efficiency on
salted road s................................... 168
Off-road driving .............................. 172
Off-road fording ............................. 170
Snow chains .................................. 333
Symmetrical low bea m.................. 112
Tire ruts ......................................... 172
Towing a trailer .............................. 212
Traveling uphill ............................... 173
Wet road surface ........................... 168
DVD audio (on-board computer) ......226
DVD video (on-board computer) ......227 E
EASY-ENTRY feature Activating/deactivating .................233
Function/notes ............................. 105
EASY-EXIT feature
Crash-responsive ........................... 106
Function/notes ............................. 105
Switching on/off ........................... 233
EBD (electronic brake force
distribution)
Display message ............................ 237
Function/notes ................................ 72 ECO display
Function/notes ............................. 167
On-board computer .......................224
ECO start/stop function
Automatic engine start ..................149
Automatic engine switch-off ..........149
Deactivating/activating .................150
General information .......................148
Important safety notes ..................148
Introduction ................................... 148
Electronic Stability Program
see ESP ®
(Electronic Stability Program)
Emergency release
Driver's door .................................... 83
Vehicle ............................................. 83
Emergency spare wheel
General notes ................................ 362
Important safety notes ..................361
Storage location ............................ 362
Stowing .......................................... 363
Technical data ............................... 364
Emergency Tensioning Devices
Function .......................................... .60
Safety guideline s............................. 43
Emergency unlocking
Tailgate ............................................ 88
Emissions control
Service and warranty information ....23
Engine
Check Engine warning lamp ........... 268
Display message ............................ 247
ECO start/stop function ................148
Engine number ............................... 367
Irregular running ............................ 151
Jump-starting ................................. 320
Starting problems ..........................151
Starting the engine with the
SmartKey ....................................... 147
Starting with KEYLESS-GO .............147
Switching off .................................. 164
Tow-starting (vehicle) ..................... 325
Engine, jump starting
see Jump starting (engine)
Engine electronics
Problem (malfunction) ...................151 Index
9

Fuse box in the engine
compartment
................................. 326
Important safety notes ..................325 G
Garage door opener Clearing the memory .....................298
Important safety notes ..................295
Opening/closing the garage door ..297
Programming (button in the rear-
view mirror) ................................... 296
Gear or selector lever (cleaning
guidelines) ......................................... 311
Genuine parts ...................................... 22
Glove box ........................................... 275
GTW (Gross Trailer Weight)
(definition) ......................................... 352H
Handbrake see Parking brake
Hazard warning lamps ......................115
Headlamps Adding fluid to cleaning system .....305
Cleaning system (function) ............115
Cleaning system (notes) ................373
Fogging up ..................................... 117
see Automatic headlamp mode
Head restraints
Adjusting ....................................... 101
Adjusting (electrically) ...................101
Adjusting (manually). .....................101
Adjusting (rear) .............................. 102
Installing/removing (rear) ..............102
see NECK-PRO head restraints/
NECK-PRO luxury head restraints
Heating
see Climate control
High-beam headlamps
Changing bulbs .............................. 120
Display message ............................ 245
Switching on/off ........................... 115
Hill start assist .................................. 148HOLD function
Deactivating ................................... 184
Display message ............................ 251
Function/notes ............................. 183
Hood
Closing .......................................... .302
Display message ............................ 259
Important safety notes ..................301
Opening ......................................... 302
Hydroplaning ..................................... 170 I
Ignition lock see Key positions
Immobilizer .......................................... 73
Indicator lamps see Warning and indicator lamps
Instrument cluster
Overview .......................................... 33
Settings ......................................... 230
Warning and indicator lamps ...........34
Instrument cluster lighting ..............231
Interior lighting ................................. 118
Automatic control ..........................118
Delayed switch-off (on-board
computer) ...................................... 232
Emergency lighting ........................119
Manual control ............................... 118
Overview ........................................ 118
Reading lamp ................................. 118
Setting the brightness of the
display/switch (on-board
computer) ...................................... 231 J
Jack Storage location ............................ 314
Using ............................................. 356
Jump starting (engine) ......................320 K
KEYLESS-GO Convenience closing feature ............91
Display message ............................ 260
Locking ............................................ 77
Start/Stop button .......................... 145 Index
11

Display message
s.......................... 235
Factory settings submenu .............234
Important safety notes ..................220
Instrument cluster submenu ..........230
Lighting submenu .......................... 231
Menu overview .............................. 223
Message memory .......................... 235
Navigation menu ............................ 225
Operation ....................................... 221
Service menu ................................. 230
Settings menu ............................... 230
Standard displa y............................ 223
Telephone menu ............................ 227
Trip menu ...................................... 223
Vehicle submenu ........................... 232
Video DVD operation .....................227
Opening and closing the side trim
panels ................................................. 121
Operating safety Declaration of conformity ................26
Important safety notes ....................25
Operating system
see On-board computer
Operator's Manual
Vehicle equipment ...........................23
Outside temperature display ...........221
Overhead control panel ......................38
Override feature Rear side windows ...........................66P
Paint code number ............................366
Paintwork (cleaning instructions) ...307
Panic alarm .......................................... 42
Panorama roof with power tilt/
sliding panel
Opening/closing .............................. 93
Opening/closing the roller
sunblind ........................................... 94
Problem (malfunction) .....................95
Resetting ......................................... 94
Panorama sliding sunroof
Important safety notes ....................92
Parking ............................................... 164
Important safety notes ..................164
Parking brake ................................ 165Position of exterior mirror, front-
passenger side ............................... 108
Rear view camera
.......................... 192
see PARKTRONIC
Parking aid
Active Parking Assist .....................188
see Exterior mirrors
see PARKTRONIC
Parking brake
Display message ............................ 237
Notes/function .............................. 165
Parking lamps
Changing bulbs .............................. 120
Switching on/off ........................... 114
PARKTRONIC
Deactivating/activating .................187
Driving system ............................... 185
Function/notes ............................. 185
Important safety notes ..................185
Problem (malfunction) ...................188
Range of the sensors .....................185
Trailer towing ................................. 187
Warning displa y............................. 186
PASSENGER AIR BAG OFF
Problem (malfunction) .....................53
Problems (malfunction) .................. 242
PASSENGER AIR BAG OFF indicator
lamp ...................................................... 49
Plastic trim (cleaning instructions) .310
Power washers .................................. 307
Power windows see Side windows
PRE-SAFE ®
(anticipatory occupant
protection) Display message ............................ 238
Operation ........................................ .54
PRE-SAFE ®
Brake
Activating/deactivating .................229
Display message ............................ 239
Function/notes ................................ 72
Warning lamp ................................. 271
Program selector button ..................155
Protection of the environment General notes .................................. 22
Pulling away
Automatic transmission .................14714
Index

Seat belts
Adjusting the driver's and front-
passenger seat belt .........................58
Adjusting the height ......................... 58
Belt force limiters ............................ 60
center rear-compartment sea t......... 59
Cleaning ......................................... 312
Correct usage .................................. 56
Emergency Tensioning Devices ....... .60
Fastening ......................................... 58
Important safety guidelines .............56
Releasing ......................................... 59
Safety guidelines ............................. 43
Switching belt adjustment on/off
(on-board computer) ......................233
Warning lamp ................................. 261
Warning lamp (function) ................... 59
Seats
Adjusting (electrically) ...................100
Adjusting lumbar support ..............102
Adjusting the 4-way lumbar
support .......................................... 103
Adjusting the head restraint ..........101
Cleaning the cover .........................311
Correct driver's seat position ........... 98
Folding the backrest (rear
compartment) forwards/back .......276
Folding the rear bench seat
forwards/back ............................... 276
Important safety notes ....................99
Seat heating problem ....................104
Storing settings (memory function) 109
Switching seat heating on/off .......103
Sensors (cleaning instructions) .......309
Service menu (on-board computer) .230
Service products Brake fluid ..................................... 372
Coolant (engine) ............................ 372
DEF special additives .....................370
Engine oil ....................................... 371
Fuel ................................................ 367
Important safety notes ..................367
Refrigerant (air-conditioning
system) .......................................... 374
Washer fluid .................................. .373
Settings
Factory (on-board computer) .........234
On-board computer .......................230Setting the air distribution
...............136
Setting the airflow ............................137
Side impact air bag .............................47
Side marker lamp (display
message) ............................................ 245
Side windows Cleaning ......................................... 308
Convenience closing feature ............90
Convenience opening feature ..........90
Important safety information ...........88
Opening/closing .............................. 89
Problem (malfunction) .....................92
Resetting ......................................... 91
Sliding sunroof
see Panorama roof with power
tilt/sliding panel
SmartKey
Changing the battery .......................79
Changing the programming .............77
Checking the battery .......................79
Convenience closing feature ............90
Convenience opening feature ..........90
Display message ............................ 260
Door central locking/unlocking .......76
Important safety notes ....................76
Loss ................................................. 80
Mechanical key ................................ 78
Positions (ignition lock) .................145
Problem (malfunction) .....................80
Starting the engine ........................147
Snow chains ...................................... 333
Sockets Center console .............................. 284
General notes ................................ 284
Rear compartment .........................285
Spare wheel
Storage location ............................ 362
Stowing .......................................... 363
Specialist workshop ............................ 27
Special seat belt retractor .................. 64
Speed, controlling see Cruise control
Speedometer
Digital ............................................ 224
In the Instrument cluster .................33
Segments ...................................... 221
Selecting the unit of measurement 230
see Instrument cluster 16
Index

V
Vanity mirror (in the sun visor) ........ 283
Vehicle Correct use ...................................... 27
Data acquisition ............................... 28
Display message ............................ 258
Emergency locking ........................... 83
Emergency unlocking .......................83
Equipment ....................................... 23
Individual settings ..........................230
Limited Warranty ............................. 28
Loading .......................................... 342
Locking (in an emergency) ...............83
Locking (SmartKey) .......................... 76
Lowering ........................................ 358
Maintenance .................................... 24
Parking for a long period ................ 165
Pulling away ................................... 147
Raising ........................................... 356
Reporting problems .........................27
Securing from rolling away ............355
Towing away .................................. 322
Transporting .................................. 324
Unlocking (in an emergency) ...........83
Unlocking (SmartKey) ......................76
Vehicle data ................................... 375
Vehicle data ....................................... 375
Vehicle data (off-road driving) Approach/departure angl e............ 376
Fording depth ................................ 375
Maximum gradient climbing ability 376
Vehicle dimensions ...........................375
Vehicle emergency locking ................83
Vehicle identification number see VIN
Vehicle identification plate ..............366
Vehicle tool kit .................................. 314
Video (DVD) ........................................ 227
VIN ...................................................... 366W
Warning and indicator lamps ABS ................................................ 263
Brakes ........................................... 263
Check Engine ................................. 268
Coolant .......................................... 269Distance warning
........................... 271
DISTRONIC PLUS ........................... 271
ESP ®
.............................................. 265
ESP ®
OFF ....................................... 266
Fuel tank ........................................ 268
Overview .......................................... 34
PASSENGER AIRBAG OFF ................49
Reserve fuel ................................... 268
Seat belt ........................................ 261
SRS ................................................ 267
Tire pressure monitor ....................272
Warranty ............................................ 366
Washer fluid Display message ............................ 259
Wheel bolt tightening torque ...........358
Wheel chock ...................................... 355
Wheels Changing a wheel .......................... 354
Checking ........................................ 331
Cleaning ......................................... 307
Cleaning (warning) .........................355
Emergency spare wheel .................361
Important safety notes ..................330
Interchanging/changing ................354
Mounting a new wheel ...................357
Mounting a wheel .......................... 355
Removing a wheel ..........................357
Storing ........................................... 355
Tightening torque ........................... 358
Wheel size/tire size .......................359
Window curtain air bag
Display message ............................ 240
Operation ........................................ .48
Windows
see Side windows
Windshield
Defrosting ...................................... 137
Windshield washer fluid
see Windshield washer system
Windshield washer system ..............305
Notes ............................................. 373
Windshield wipers
Problem (malfunction) ...................126
Rear window wiper ........................123
Replacing the wiper blades ............123
Switching on/off ........................... 12220
Index

Protection of the environment
General notes
H
Environmental note
Daimler's declared policy is one of
comprehensive environmental protection.
The objectives are for the natural resources
that form the basis of our existence on this
planet to be used sparingly and in a manner
that takes the requirements of both nature
and humanity into account.
You too can help to protect the environment
by operating your vehicle in an
environmentally responsible manner.
Fuel consumption and the rate of engine,
transmission, brake and tire wear are affected
by these factors:
R operating conditions of your vehicle
R your personal driving style
You can influence both factors. You should
bear the following in mind:
Operating conditions:
R avoid short trips as these increase fuel
consumption.
R always make sure that the tire pressures
are correct.
R do not carry any unnecessary weight.
R remove roof racks once you no longer need
them.
R a regularly serviced vehicle will contribute
to environmental protection. You should
therefore adhere to the service intervals.
R always have service work carried out at a
qualified specialist workshop.
Personal driving style:
R do not depress the accelerator pedal when
starting the engine.
R do not warm up the engine when the vehicle
is stationary.
R drive carefully and maintain a safe distance
from the vehicle in front.
R avoid frequent, sudden acceleration and
braking. R
change gear in good time and use each gear
only up to 00C3of its maximum engine speed.
R switch off the engine in stationary traffic.
R keep an eye on the vehicle's fuel
consumption. Environmental concerns and
recommendations
Wherever the operating instructions require
you to dispose of materials, first try to
regenerate or re-use them. Observe the
relevant environmental rules and regulations
when disposing of materials. In this way you
will help to protect the environment. Genuine Mercedes-Benz parts
H
Environmental note
Daimler AG also supplies reconditioned major
assemblies and parts which are of the same
quality as new parts. They are covered by the
same Limited Warranty entitlements as new
parts.
! Air bags and Emergency Tensioning
Devices, as well as control units and
sensors for these restraint systems, may be
installed in the following areas of your
vehicle:
R doors
R door pillars
R door sills
R seats
R cockpit
R instrument cluster
R center console
Do not install accessories such as audio
systems in these areas. Do not carry out
repairs or welding. You could impair the
operating efficiency of the restraint
systems. 22
Introduction

Have aftermarket accessories installed at
a qualified specialist workshop.
You could jeopardize the operating safety of
your vehicle if you use parts, tires and wheels
as well as accessories relevant to safety
which have not been approved by Mercedes.
This could lead to malfunctions in safety-
relevant systems, e.g. the brake system. Use
only genuine Mercedes-Benz parts or parts of
equal quality. Only use tires, wheels and
accessories that have been specifically
approved for your vehicle.
Genuine Mercedes-Benz parts are subject to
strict quality control. Every part has been
specifically developed, manufactured or
selected for and adapted to Mercedes-Benz
vehicles. Only genuine Mercedes-Benz parts
should therefore be used.
More than 300,000 different genuine
Mercedes-Benz parts are available for
Mercedes-Benz models.
All authorized Mercedes-Benz Centers
maintain a supply of genuine Mercedes-Benz
parts for necessary service and repair work.
In addition, strategically located parts
delivery centers provide quick and reliable
parts service.
Always specify the vehicle identification
number (VIN) (Y page 366) when ordering
genuine Mercedes-Benz parts. Operator's Manual
Vehicle equipment
This Operator's Manual describes all models
and all standard and optional equipment of
your vehicle available at the time of going to
print. Country-specific differences are
possible. Bear in mind that your vehicle may
not feature all functions described here. This
also applies to safety-relevant systems and
functions. The equipment in your vehicle may
therefore differ from that shown in the
descriptions and illustrations. The original purchase agreement lists all
systems installed in your vehicle.
Should you have any questions concerning
equipment and operation, please consult an
authorized Mercedes-Benz Center.
The Operator's Manual and Maintenance
Booklet are important documents and should
be kept in the vehicle. Service and vehicle operation
Service and literature
Your vehicle is covered under the terms of the
warranties printed in the Service and
Warranty Information booklet. Your
authorized Mercedes-Benz Center will
exchange or repair any defective parts
originally installed in the vehicle in
accordance with the terms of the following
warranties:
R New Vehicle Limited Warranty
R Emission Systems Warranty
R Emission Performance Warranty
R California, Connecticut, Maine,
Massachusetts, New York, Pennsylvania,
Rhode Island and Vermont Emission
Control Systems Warranty
R State warranty enforcement laws (lemon
laws) Introduction
23 Z