Smart Smart 451 Owner’s Manual

,

Introduction of the smart fortwo
Model series 451

Introduction into Service Manual

www.smartusa.com

Introduction of the smart fortwo  Model series 451

SN_Typ 451_us.book Seite 1 Freitag, 30. November 2007 1:56 13

Introduction of the smart fortwo

Model Series 451

Introduction into Service Manual

smart USA

SN_Typ 451_us.book Seite 2 Freitag, 30. November 2007 1:56 13

Copyright

© smart USA, 2007

All rights reserved. Reproduction by any means,
electronic or mechanical, including photocopying,
recording, or by any information storage and retrieval
system or translation in whole or part is not permitted
without written authorization from the publisher.

Published by smart USA, 2007
Printed in U.S.A.

www.smartusa.com

SN_Typ 451_us.book Seite 3 Freitag, 30. November 2007 1:56 13

Content

Preface 7

Complete vehicle

Overview

Technical data 10

Maintenance 13

Safety concept 17

Electrical system

Onboard electrical system/power supply 20

Complete networking 22

Wiring harnesses 24

Diagnosis 26

SAM control unit 28

8

Engine M132

Engine description 30

Performance graph 30

Engine data 32

Valve assembly 33

Valve timing 34

Gasoline injection and ignition system 35

Belt drive 38

Cooling system 39

Engine mount 41

Introduction of the smart fortwo, Model Series 451

3

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Content

Fuel system

Fuel supply

42

Exhaust system

Overview 45

Secondary air injection 46

Automated manual transmission

Transmission description 47

Transmission data 48

Shift mechanism 49

Synchronization 54

Transmission control 55

Park pawl 61

Clutch 62

Chassis

Front axle 64

Rear axle 65

Rear module 66

Tire pressure monitor 67

Brakes 69

Steering 75

4

Introduction of the smart fortwo, Model Series 451

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Content

Body

Interior

82

Doors/flaps 86

Roof systems 90

Central locking 96

Antitheft alarm system (ATA [EDW]) 99

Exterior lights 101

Audio system 102

Climate control 104

Customized Bodypanel System (CBS) 106

Seats 108

Supplemental restraint system 109

Body 113

Accessories

smart accessories 116

Index 120

Introduction of the smart fortwo, Model Series 451

5

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Content

6

Introduction of the smart fortwo, Model Series 451

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Dear reader,

Preface

This Introduction into Service Manual presents the
new smart fortwo in model series 451.

The purpose of this manual is to inform you of the
technical features of this new vehicle. This brochure
is intended to provide information for people
employed in service, maintenance and repair as well
as for aftersales staff.

In terms of the contents, the emphasis in this Intro
duction into Service manual is on presenting the major
assemblies and systems.

This Introduction into Service manual is not intended
as an aid for repairs or for the diagnosis of technical
problems. For such needs, more extensive information
is available in the Workshop Information System (WIS)
and in the Diagnosis Assistance System (DAS).

WIS is updated monthly. Therefore, the information
available there reflects the latest technical status.

This Introduction into Service Manual presents initial
information relating to the new smart fortwo in model
series 451 and, as such, is not stored in WIS. The
contents of this brochure are not updated. No provi
sion is made for supplements.

We will publicize modifications and new features in the
relevant WIS documents. The information presented in
this Introduction into Service Manual may therefore
differ from the more uptodate information found in
WIS.

All information relating to technical data, equipment
and options is valid as of the copy deadline in
September 2007 and may therefore differ from the
current production configuration.

smart USA aftersales

Introduction of the smart fortwo, Model Series 451

7

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Overview

Complete vehicle

smart fortwo coupé

P00.10-4192-00

smart fortwo cabrio

P00.10-4198-00

8

Introduction of the smart fortwo, Model Series 451

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Vehicle concept

Overview

Externally, the smart fortwo is immediately distin
guishable by its compactness with the tridion safety
cell and its twotone design. The smart fortwo is avail
able in a variety of colors. The tridion safety cell in
black or silver can be combined with six different
basic colors.

The model series can be ordered as the smart fortwo
coupé or the smart fortwo cabrio.

Vehicle characteristics

• Overall vehicle exterior
External dimensions to suitably accommodate the
occupants and provide sufficient the trunk
capacity.
Plastic panoramic sunroof or full roof on the smart
fortwo coupé.
Tritop soft top on the smart fortwo cabrio.

• Overall vehicle interior
Numerous color and pattern variants in the
interior.
Ergonomic instrument cluster in the instrument
panel.
Clearly arranged and userfriendly center
console.
Rearend door with integral stowage compartment
for the smart fortwo coupé or tightfitting stowage
areas without retaining straps for the roof side
supports in the smart fortwo cabrio.

• Engine/injection system
3cylinder gasoline engine with 52 kW.
Fuel injection system with Bosch MultiPoint
Injection.

• Transmission
5speed automated manual transmission AMT 2
(2nd generation).

Despite its compact appearance, the smart fortwo
provides the occupants with a generous amount of
legroom and sufficient trunk capacity.

The interior compartment has a classic design. The
instrument panel was designed with straight lines and
the colors have been kept refined. Repeated aluminum
accent trim on the air vents and the inside door
handles gives the interior design a harmonic yet
modern aspect.

• Suspension
MacPherson front suspension with torsion
stabilizer bars.
DeDion rear axle.

• Brake
Hydraulic 2circuit brake system with ESP and TT
(front/rear) split, version 8.1 from Bosch.

• Steering
Equipped with rackandpinion steering as
standard.
Electromechanical power steering with active
steering centering and adaptation of the steering
forces available as special equipment.

• Maintenance
Maintenance concept: Maintenance service only
every two years, with only the Oil Service Plus once
a year in between.
Service flap at front for easy access to the
maintenance points.

•Safety
Restraint system with airbags and emergency
tensioning retractors.
Bodyshell made of highstrength steels.
Door reinforcements made of highstrength
steels.
Fulllength knee guard for driver and passenger.

Complete vehicle

Introduction of the smart fortwo, Model Series 451

9

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Technical data

Complete vehicle

60.7

16.7

50.5

69.0

11. 5

73.5

106.1

50.0

21. 0

21. 0

54.5

61. 4

39.7

27 .7

19.7

24.4

28.7

15.9

10

48.0

P00.10-4259-00

Dimensions  smart fortwo coupé

Dimensions Unit smart fortwo coupé (model 451)

Vehicle length in (mm) 106.1 (2695)

Vehicle width in (mm) 61.4 (1559)

Vehicle height in (mm) 60.7 (1542)

Wheelbase in (mm) 73.5 (1867)

Front track width in (mm) 50.5 (1283)

Rear track width in (mm) 54.5 (1385)

Introduction of the smart fortwo, Model Series 451

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Technical data

60.7

Complete vehicle

16.7

50.5

69.0

11. 5

73.5

106.1

50.0

21. 0

21. 0

54.5

61. 4

39.7

27 .7

19.7

24.4

28.7

15.9

48.0

P00.10-4260-00

Dimensions  smart fortwo cabrio

Dimensions Unit smart fortwo cabrio (model 451)

Vehicle length in (mm) 106.1 (2695)

Vehicle width in (mm) 61.3 (1559)

Vehicle height in (mm) 60.7 (1542)

Wheelbase in (mm) 73.5 (1867)

Front track width in (mm) 50.5 (1283)

Rear track width in (mm) 54.5 (1385)

Introduction of the smart fortwo, Model Series 451

11

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Technical data

Models and major assemblies

smart fortwo Model Engine Transmission

smart fortwo coupé 451.331

Complete vehicle

smart fortwo cabrio 451.431

Loads, weights and other data

Powerplant kW 52 52

132.910 (52 kW) 717.482

Unit smart fortwo coupé smart fortwo cabrio

Permissible front axle load lb

(kg)

Permissible rear axle load lb

(kg)

Curb weight as per DIN lb

(kg)

Permissible gross vehicle weight lb

(kg)

Payload lb

(kg)

of which max. in luggage compart
ment

Max. seating capacity 2

Luggage compartment volume

up to belt line

up to roof

lb

(kg)

in

(l)

in

(l)

3

3

1652
(820)

2247

(1050)

595

(230)

969

(440)

1458

(660)

110

(50)

7.8

(220)

12

(340)

1740
(840)

2247

(1050)

507

(210)

12

Turning circle yd

(m)

Tank capacity/including reserve US gal

(l)

Introduction of the smart fortwo, Model Series 451

9.57

(8.75)

8.72/1.32
33/5

SN_Typ 451_us.book Seite 13 Freitag, 30. November 2007 1:56 13

Ma xintenance concept

Consistent product development has enabled a
futureoriented servicing concept to be implemented
in model series 451.

Maintenance

The servicing concept of the smart fortwo has allowed
the service intervals to be extended significantly, as
shown below.

Maintenance intervals

smart fortwo kW Interval

Gasoline engine 52 Every 2 years or 20,000 miles*

* depending on first occurrence

Oil Service Plus

Complete vehicle

In combustion engines with a high engine output per
unit of displacement, the engine oil is subjected to
extreme loads. With 3.7 US qt (3.5 liters), the smart
fortwo has a relatively small quantity of engine oil,
meaning that it has to be replaced at regular
time/mileage intervals.

To help optimize operating costs, the "Oil Service
Plus" has been introduced, which is due every 10 000
miles or once per year. It comprises merely an engine
oil change and inspection of the safetyrelevant
components and functions.

This servicing concept has benefits for both the
workshops and the customers:

• Customers have lower vehicle operating costs due
to the reduced maintenance costs as a whole. This
improves customer satisfaction.

• The workshops improve their competitiveness in
the servicing business especially. Longerlasting
customer loyalty and better chances of followup
business are possible with this concept.

Introduction of the smart fortwo, Model Series 451

13

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Maintenance

Maintenance interval display (WIA)

The maintenance interval display is located in the
multifunction display of the instrument cluster.

The maintenance intervals are indicated by the

Complete vehicle

lighting of one or two wrench symbols.

In addition, approximately one month in advance of a
scheduled service date the multifunction display
shows the remaining time (in days) until it is due. After
engine start the range (in miles) is displayed for about
ten seconds.

i Note

When the Oil Service Plus or a maintenance service
has been performed, the maintenance interval
display can be reset to the starting distance on
the instrument cluster itself or via STAR
DIAGNOSIS.
(See WIS for a detailed description.)

Meaning of wrench symbols:

•1 wrench means Oil Service Plus

• 2 wrenches mean maintenance service

Instrument cluster

P54.32-5676-00

A1 Instrument cluster
A1p13 Multifunction display

14

Multifunction display with maintenance interval display

P54.32-5677-00

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Maintenance

Service flap

The smart fortwo is equipped with a detachable
service flap which allows convenient access to all
maintenance points in the front section. Customer
relevant maintenance items can be performed by the
customer accordingly.

To remove the service flap, levers located in the air
grille on each side must be operated to unlock the
service flap. The service flap can then be removed
and suspended by two brackets on the front of the
vehicle. A check strap prevents the service flap from
falling down.

Maintenance points at front end

The most important maintenance points at the front of
the car are:

• Brake fluid reservoir

• Windshield washer fluid reservoir

• Coolant expansion reservoir

• Lamp units for bulb replacement

Complete vehicle

Maintenance points at front end

1 Brake fluid reservoir
2 Windshield washer fluid reservoir
3 Coolant expansion reservoir

4 Lamp unit for bulb replacement
5Service flap
6 Check strap

Introduction of the smart fortwo, Model Series 451

P00.20-2629-00

15

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Maintenance

Maintenance points in engine compartment

The maintenance points in the engine compartment
can be accessed once the engine compartment cover
in the luggage compartment floor has been removed.

Complete vehicle

The most important maintenance points in the engine
compartment are:

•Oil filler neck

•Oil dipstick

•Air filter housing

• Spark plugs

16

Maintenance points in engine compartment

7 Oil filler neck
8 Oil dipstick

Introduction of the smart fortwo, Model Series 451

P00.20-2630-00

9 Air filter housing

10 Ignition coils (spark plugs)

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In the smart fortwo, high levels of active safety are
provided by both triedandtested and newly devel
oped systems and components.

Active safety

Safety concept

Complete vehicle

Active safety includes measures and equipment that
help to prevent detected dangers from occurring in
the first place, or that warn the driver of dangers in
advance, or that assist him in critical driving situa
tions:
A distinction is drawn between the following safety
aspects:

•Driving safety

• Stressreducing safety

•Perceptual safety

• Operating safety

The components responsible for maintaining driving
safety include:

• Electromechanical power steering (SA)

• 5speed automated manual transmission

• Vehicle dynamics systems:
ABS (antilock brake system)
ASR (acceleration skid control)
ESP (electronic stability program)

High levels of stressreducing safety are due to:

• Comfortable seats with integral head restraints

• Temperatureregulated air conditioning

High levels of perceptual safety are assured by
the following components:

•Auto on/off headlamps (SA)

• Center highmounted brake lamp in the roof
spoiler

Operating safety is provided by:

• Ergonomically designed driver area

• Clearly arranged and easily reachable controls

Introduction of the smart fortwo, Model Series 451

17

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Safety concept

Passive safety

The goal of a vehicle's passive safety is to minimize as
much as possible the effects of an accident on the
people involved. Some of the most important aspects
of this are the preservation of the survival space

Complete vehicle

(rigid passenger cell), high energy dissipation in the
event of an accident thanks to exploitable crumple
zones at the front and rear, and energyabsorbing
restraint systems in the interior.

The passive safety concept includes:

• tridion safety cell consisting of 50% highstrength
steel

• Crash management system (CMS) at the front and
rear, which absorbs energy at low vehicle speeds
and prevents expensive bodyshell damage

• Front end with no major assemblies, for effective
exploitation of the short overhang as a crumple
zone

• Inclusion of the wheels and axles/frametype
integral support in the crumple zone and for force
application

• Front and rear structures with several impact
planes and large cross sections to transfer and
disperse the crash energy that is generated

• Long forward displacement area for the driver and
passenger with restraint systems adapted to
compensate for the "short" crumple zone

• Sturdy steel seat structures for effective
protection against shifting cargo and for specific
deformation in rearend collisions

• Side doors made of solid steel frame profiles
including side impact protection

• Safe positioning of the fuel tank in the underfloor
area between the axles

• Deformable steering column to dissipate energy,
prevent intrusion and lengthen the forward
displacement distance in a frontal collision

• Full interior lining to reduce head injuries

The occupant restraint systems comprise:

• 2stage driver airbag in steering wheel

• 2stage topmounted passenger airbag with
deployment opening on the top surface of the
instrument panel

• Head/thoraxbags in the backrests

• Threepoint seat belts with emergency tensioning
retractors, belt force limiters and belt guides on
the backrests

• Seat belt reminders for driver and passenger

• Belt tension sensor on passenger side

• Passenger seat with Weight Sensing System (WSS)
with automatic passenger airbag deactivation for
the corresponding weight classes and airbag OFF
indicator lamp

• Fulllength knee guard

• Two frontal acceleration sensors on front
crossmember

• Two satellite sensors on inner side wall in area of
left and right Bpillar

• Restraint systems control unit

18

1 Driver airbag

P91.60-3663-00

2 Passenger airbag
3 Head/thoraxbag

Introduction of the smart fortwo, Model Series 451

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Protective measures for pedestrians and cyclists
comprise:

• Singlepiece front end module

• Main headlamps with predetermined fracture point

• Concealed and retracting windshield wiper shafts

• Energyabsorbing covering on the center piece in
front of the windshield

• Large, soft plastic surfaces at the front

The extended range of functions following an accident
includes:

• Automatic engine off feature

• Interruption of the fuel supply

• Unlocking of the doors

• Activation of the hazard warning system

Safety concept

Complete vehicle

Introduction of the smart fortwo, Model Series 451

19

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Onboard electrical system/power supply

General

The onboard electrical system ensures that the
power supply to all the electrical consumers and
components in the vehicle is appropriate for the
requirements and the situation.

Electrical system

The onboard electrical system consists of the
following main components:

•Starter

•Battery

•Alternator

• MESFI [ME] control unit

• Instrument cluster

Starter

The starter has an output of 0.95 kW and supplies the
torque necessary to start the engine. It takes the
necessary energy from the adequately charged
battery.

Battery

The battery (42 Ah) supplies the consumers when the
engine is off, the starter while the engine is being
started, and the onboard electrical system when the
alternator is unable to provide the required consumer
current.

The battery is located in the passenger footwell under
the carpeting.

There are three fuses located in the area of the
battery:

F36 Secondary air injection pump fuse
F58 Starter/alternator fuse
F91 SAM prefuse

20

G1 Battery

P54.10-2890-00

F36 Secondary air injection pump fuse
F58 Starter/alternator fuse
F91 SAM prefuse

Introduction of the smart fortwo, Model Series 451

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Onboard electrical system/power supply

Alternator

The alternator supplies the electrical consumers
while the engine is running and recharges the battery
so that a subsequent engine start is possible.
The alternator is equipped with an overvoltage
protection function that limits the onboard power
supply voltage in the event of a defect in the
governor. The alternator is monitored by the MESFI
[ME] control unit.

The alternator is preexcited via a direct line. The
alternator load is reported back to the MESFI [ME]
control unit over a separate line and monitored.

Instrument cluster

The onboard power supply voltage is monitored by
the engine control. If the voltage is < 11.5 V for a
period of over 3 min, a signal is sent over CAN to the
instrument cluster and the alternator charge moni
toring and warning lamp (A1e5) lights up.

Electrical system

G2 Alternator

P54.10-2891-00

A1 Instrument cluster
A1e5 Alternator charge monitoring and warning lamp

Introduction of the smart fortwo, Model Series 451

P54.32-5684-00

21

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Complete networking

Overall network  location of components

Electrical system

Overall network  full equipment

A1 Instrument cluster

on the left side of the instrument panel

A15p4 Tachometer

(with code (V31) Cockpit clock and tachome
ter package)
in the center of the instrument panel

B24/15 Yaw rate, lateral and longitudinal accelera

tion sensor
under the floor covering near the driver
seat

B32 ATA [EDW] microwave sensor

(with code (V01) Antitheft alarm system
(FFO)) under the center console near the
handbrake lever

P00.19-4338-00

B38 Rain sensor/light sensor

(with code (V54) Rain/light sensor)
in the middle of the windshield near the in
side rearview mirror

H3/2 Alarm siren with inclination sensor

(with code (V01) Antitheft alarm system
(FFO)) on the right in front of the fuel tank

N2/7 Restraint systems control unit

in the center under the instrument panel

N3/10 MESFI [ME] control unit

behind the right side paneling in the rear

N10/10 SAM control unit

on the left under the instrument panel

N15/5 Electronic selector lever module control

unit

(Legend continued on the next page)

22

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Overall network  CAN bus/LIN bus

Complete networking

Electrical system

Block diagram  Full equipment

N15/6 Automated manual transmission control unit

under the floor covering near the driver
seat

N23 Heater/AC operating unit

(with code (I01) Air conditioning Plus and
code (V30) Outside temperature sensor
(FFO))
in the center of the instrument panel

N25/5 Front HS [SIH] control unit

(with code (S17) Seat heaters (FFO))
in the center under the instrument panel

N475 ESP control unit

on ESP hydraulic unit

N49 Steering angle sensor in steering wheel

P00.19-4339-00

N57/2 Power window convenience feature control

unit
(with code (V43) Power windows)
on the left under the instrument panel

N68 Power steering control unit

(with code (V26) Power steering, EPS (FFO))
in interior compartment on left of firewall

N88 TPM [RDK] control unit

on left below instrument panel

N110 Weight Sensing System (WSS) control unit

on underside of passenger seat

X11/4 Data link connector

on the bottom of the instrument panel on the
driver side

CAN Controller Area Network bus

(data bus/CAN bus)

CANB Controller Area Network bus class B

(interior compartment)
LIN B Interior Local Interconnect Network 1
LIN C Interior Local Interconnect Network 2

Introduction of the smart fortwo, Model Series 451

23

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Wiring harnesses

Electrical system

Wiring harness groups

The wiring harness is divided into the following groups:

1 Main wiring harness
2 Engine wiring harness
3 Transmission wiring harness
4 Battery wiring harness

P54.18-4507-00

Not illustrated:

 Door wiring harness
 Soft top wiring harness (in smart fortwo cabrio)
 Rearend door wiring harness

24

Introduction of the smart fortwo, Model Series 451

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Wiring harnesses

General

The wiring harness variants result from the basic
standard equipment, the special equipment items and
the national versions.

Repair capability

A basic wiring harness repair kit in a case is available
for repairing individual lines, wiring harnesses and
connectors without sealed plugs. All the above
repairs can be carried out using this kit.

Electrical system

It is also possible to expand the kit with a supple
mental repair set to allow wiring harnesses with
sealed plugs to be repaired.

i Note

W000 589 13 99 00

Basic wiring harness repair kit.
Tools for repairing individual lines, wiring
harnesses and connectors in combination with the
wiring harness repair kit supplement for
passenger cars (W220 589 04 99 00).

W220 589 04 99 00

Wiring harness repair kit supplement for
passenger cars
Tools for repairing individual lines, wiring
harnesses and connectors in combination with the
basic wiring harness repair kit (W000 589 13 99

00).

Introduction of the smart fortwo, Model Series 451

Wiring harness repair kit

P54.18-4140-00

25

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Diagnosis

General

The network architecture in model 451 allows external
access to individual control units in the CAN bus
system.

Electrical system

Data link connector

The CAN bus is accessed by means of a diagnostic
tester that is connected to the vehicle via the data link
connector. The data link connector is linked directly
to the CAN bus and can therefore access all the
control units that have diagnostic or programming
capability. The data link connector is located in the
vehicle interior on the underside of the instrument
panel on the driver side.

Diagnostic tester

By connecting the diagnostic tester, the vehicle with
all its equipment variants can be precisely identified.
This enables accurate fault evaluation and rectifica
tion and the analysis of vehiclespecific values and
parameters.

26

Location of data link connector (X11/4)

P54.22-2048-00

Introduction of the smart fortwo, Model Series 451

SN_Typ 451_us.book Seite 27 Freitag, 30. November 2007 1:56 13

Diagnosis

Diagnosis capability

The following control units have diagnosis capability:

• Instrument cluster

• Restraint systems control unit

• WSS control unit

• MESFI [ME] control unit

•SAM control unit

• Automated manual transmission control unit

• Heater/AC operating unit

•ESP control unit

• Steering assist control unit

• TPM [RDK] control unit

• Electronic selector lever module control unit

Fault memory

Each of the control units listed above has a fault
memory that provides information about the associ
ated systems. The stored faults are displayed by the
diagnostic tester and must be rectified. When all the
faults have been eliminates, the fault memory must be
erased and read out again. There should be no fault
entries left afterwards.

Maintenance intervals

TAN generator

For the following applications a TAN (transaction
number) must be generated:

• Retrofitting the steering wheel gearshift (SAL)

• Replacing the MESFI [ME] control unit

• Replacing the SAM control unit

• Teachin of transmitter keys (after loss or
detection of additional transmitter keys)

i Note

Up to six transmitter keys in total can be taught in
at the same time.

Electrical system

The diagnostic tester is used to reset the mainte
nance interval in the instrument cluster following an
Oil Service Plus or a maintenance service.

Programming control units

The following control units can be programmed:

• MESFI [ME] control unit

•SAM control unit

• Automated manual transmission control unit

•ESP control unit

SCN (Software Calibration Number) coding

The following control units can be coded via the SCN
coding process:

• MESFI [ME] control unit

•SAM control unit

•ESP control unit

• Automated manual transmission control unit

•Restraint systems control unit

• Instrument cluster

*) The control unit is relevant to exhaust emissions,
i.e. the SCN is written in the control unit and can be
interrogated. For the other control units a virtual SCN
is generated during the coding process, but this is not
written to the control unit.

*)

*)

Introduction of the smart fortwo, Model Series 451

27

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SAM control unit

Almost all of the fuses in model 451 are accommodated
on the SAM control unit. Slots 131 are located on the
front of the SAM control unit; slots 3235 are located
on the rear.
The following fuses are not accommodated on the SAM
control unit:

Electrical system

• Secondary air injection pump fuse (F36)

• Starter/alternator fuse (F58)

• SAM prefuse (F91)

The SAM control unit is installed in the vehicle interior
on the left side near the Apillar under the instrument
panel.

The SAM control unit is linked with the CAN in order to
exchange data. It communicates with the following
components:

• Instrument cluster

• ESP control unit

• Restraint systems control unit

•MESFI [ME] control unit

• Heater/AC operating unit

• Steering assist control unit

•TPM [RDK] control unit

• Weight Sensing System (WSS) control unit

• Yaw rate, lateral and longitudinal acceleration
sensor

• Steering angle sensor

• Data link connector

28

SAM control unit (front)

P54.21-2702-00

Introduction of the smart fortwo, Model Series 451

SN_Typ 451_us.book Seite 29 Freitag, 30. November 2007 1:56 13

SAM control unit

The SAM control unit also communicates over:

• LIN B with the tachometer and the rain sensor/light
sensor

• LIN C with the ATA [EDW] microwave sensor and the
alarm siren with inclination sensor.

The fuse and relay box is integrated in the SAM
control unit.

The following relays are not accommodated on the SAM
control unit:

• Left turn signal/brake light relay (K52/11)

• Right turn signal/brake light relay (K52/12)

• Secondary air injection pump relay (K64)

• Soft top opening relay (K66/1) (only cabrio)

• Soft top closing relay (K66/2) (only cabrio)

i Note

Up to six transmitter keys can be stored in the
SAM control unit.

Electrical system

SAM control unit (rear)

Introduction of the smart fortwo, Model Series 451

P54.21-2703-00

29

SN_Typ 451_us.book Seite 30 Freitag, 30. November 2007 1:56 13

Engine description

Engine M132

At market launch, the smart fortwo is available with a

Engine M132

3cylinder gasoline engine with 61 in
displacement and 52 kW

3

(999 cm3)

30

3cylinder gasoline engine (M132)

P01.10-2942-00

Introduction of the smart fortwo, Model Series 451

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Power and torque graph

The red characteristic represents the power curve
(P) in relation to the engine speed (n).
The blue characteristic represents the torque curve
(M) in relation to the engine speed (n).

Performance graph

Engine M132

M (lb-ft) P (kW)

180
160
140
120
100

80
60
40
20

0

0 1000 2000 3000 4000 5000 6000 7000

70

60

50

40

30

20

10

0

n (1/min)

Power and torque graph M132

MTorque (lbft)

PEngine power (kW)
n Engine speed (rpm)

Introduction of the smart fortwo, Model Series 451

P01.00-2999-00

31

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Engine data

M132

Engine M132

Engine model designation 132.910

Rated output kW

Rated torque lbft (Nm)

Compression ratio e 10.0:1

Engine configuration/no. of cylinders Inline/3

Camshaft configuration/number Overhead/2

Displacement in

Bore in

at rpm

at rpm

3

(cm3)

(mm)

52

5800

68 (92)

4500

61

(999)

2.83
(72)

Stroke in

(mm)

Cylinder angle ° 45

Fuel * Premium gasoline

Emission regulations ULEV

* Fuel requirements:

Only unleaded premium fuel may be used. The octane
number (shown on the gasoline pump) should be at
least 91. This is an average value based on tests of the
octane number (RON) and motor octane number (MON)
(RON+MON/2). It is also known as the antiknock
index.

3.22

81.8

unleaded

32

Introduction of the smart fortwo, Model Series 451

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Valve assembly

Valve assembly

The timing chain is driven by the crankshaft via the
crankshaft gear and thus drives the intake camshaft
via the camshaft adjuster and the exhaust camshaft
via the exhaust camshaft sprocket. The timing chain is
guided by a slide rail. A tensioning rail and chain
tensioner ensure that the chain is at the right tension
to prevent wear and noises.

The intake and exhaust camshafts control the gas
exchange in the engine via the intake and exhaust
valves. Variable camshaft adjustment allows for
greater torque at low engine speeds and better
response time in the idle and partialload ranges. At
the same time, the camshaft adjustment helps to
achieve the stipulated exhaust emissions limits.

Engine M132

Valve assembly

1 Exhaust camshaft sprocket
2 Exhaust camshaft
3 Camshaft adjuster
4 Intake camshaft
5 Crankshaft gear
6 Crankshaft

7 Timing chain
8 Intake valve

9 Exhaust valve
10 Valve spring
11 Cup tappet

Introduction of the smart fortwo, Model Series 451

P05.00-2082-00

33

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Valve timing

General

Engine M132 is equipped with mechanical cup tappets.

Engine M132

The mechanical stress on the cams and cup tappets
makes it necessary to check and adjust the valve clea
rance.

The cup tappets must be measured using a micro
meter.

Find and insert the appropriate cup tappet by refer
ence to its markings.
The valve clearance is adjusted by exchanging the cup
tappets. These are available in various thicknesses.

34

1 Cylinder head
2 Camshaft bearing cap
3 Intake camshaft
4 Exhaust camshaft
5 Cup tappet
6 Intake valve

Introduction of the smart fortwo, Model Series 451

P05.30-2151-00

7 Exhaust valve
8 Valve spring retainer

9Valve locks
10 Valve spring
11 Valve stem seal
12 Valve seat

SN_Typ 451_us.book Seite 35 Freitag, 30. November 2007 1:56 13

Injection control

Gasoline injection and ignition system

Engine M132 features an ME (motor electronics)
gasoline injection and ignition system. The central
control unit of this system is the MESFI [ME] control
unit. It is networked over CAN with the following
components:

• Instrument cluster

•SAM control unit

• Automated manual transmission control unit

• Heater/AC operating unit

•ESP control unit

• Steering assist control unit

• Data link connector

The MESFI [ME] control unit puts its information on
the CAN, making it accessible to all the other
networked components on the CAN. The information
from other components reaches the MESFI [ME]
control unit in the same way. For example, the signal
from the clutch motor, which is read directly by the
automated manual transmission control unit, reaches
the MESFI [ME] control unit in this way.

Direct input signals come from:

Direct output signals go to:

• Fuel pump relay

• Fuel pump with fuel level sensor

• Secondary air injection pump relay

• Secondary air injection pump

• Secondary air injection pump switchover valve

• Throttle valve actuator

• Cylinder 1 ignition coil

• Cylinder 2 ignition coil

• Cylinder 3 ignition coil

• Outside air shutoff valve

• Adjustable camshaft timing solenoid

• Cylinder 1 fuel injection valve

• Cylinder 2 fuel injection valve

• Cylinder 3 fuel injection valve

• Fuel tank vent valve

There are also the following inputs on the MESFI [ME]
control unit:

• Circuit 15

• Circuit 30

• Circuit 31

Engine M132

• Knock sensor

• Fuel tank pressure sensor

• Camshaft Hall sensor

• Coolant temperature sensor

• Accelerator pedal sensor

• O2 sensor downstream of TWC [KAT]

• O2 sensor upstream of TWC [KAT]

• Crankshaft position sensor

• Throttle valve actuator

• Oil pressure switch

Function

The engine is controlled according to load by the
performance map based on the signals arriving either
directly or over CAN. The actuators are actuated via
direct lines in accordance with the values computed
by the MESFI [ME] control unit. Information intended
for other components is put on the CAN.

The MESFI [ME] control unit has an integral fault
memory and can exchange information with STAR
DIAGNOSIS via a data link connector that is connected
to the CAN.

Introduction of the smart fortwo, Model Series 451

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Gasoline injection and ignition system

Engine M132

36

Data flow chart of M132 injection system

P07.61-3578-00

Introduction of the smart fortwo, Model Series 451

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Gasoline injection and ignition system

15/30/31 Circuit status

A1 Instrument cluster
A16 Knock sensor
B4/3 Fuel tank pressure sensor
B6/1 Camshaft Hall sensor
B11/4 Coolant temperature sensor
B28 Intake manifold pressure sensor
B37 Accelerator pedal sensor
G3/1 O2 sensor downstream of TWC [KAT]
G3/2 O2 sensor upstream of TWC [KAT]
K27 Fuel pump relay
K64 Secondary air injection pump relay
L5 Crankshaft position sensor
M3/3 Fuel pump with fuel level sensor
M16/6 Throttle valve actuator
M33 Secondary air injection pump
N3/10 MESFI [ME] control unit

N10/10 SAM control unit
N15/6 Automated manual transmission

control unit
N23 Heater/AC operating unit
N475 ESP control unit
N68 Steering assist control unit
S41/1 Oil pressure switch
T1/1 Cylinder 1 ignition coil
T1/2 Cylinder 2 ignition coil
T1/3 Cylinder 3 ignition coil
X11/4 Data link connector
Y32 Secondary air injection pump switchover

valve
Y49 Adjustable camshaft timing solenoid
Y50 Outside air shutoff valve
Y58 Tank vent valve
Y62/1 Cylinder 1 fuel injection valve
Y62/2 Cylinder 2 fuel injection valve
Y62/3 Cylinder 3 fuel injection valve

CAN Controller Area Network

(data bus/CAN bus)

Engine M132

Introduction of the smart fortwo, Model Series 451

37

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Belt drive

Belt adjustment and description of stretch belt

Selftensioning belt drive

Engine M132

The alternator and coolant pump are driven by a poly
V belt with tensioning device.

The polyV belt is tensioned via a new springloaded
tensioning device. To install and remove the polyV
belt the tensioning device must be rotated clockwise
using a special tool to slacken the tension in the belt
drive. The tensioning device can then be locked in
place and the polyV belt removed.

Stretch belt

The refrigerant compressor is driven by a stretch
belt.

The stretch belt does not need a tensioning device,
but it must be replaced after a specified mileage. It is
removed and installed with the aid of a special tool
that guides the stretch belt over the belt pulley of the
refrigerant compressor. The stretch belt can be
pulled on or off the belt pulley by cranking the engine
in its normal direction of rotation.

38

Belt drive

1 Alternator belt pulley
2 PolyV belt
3 Coolant pump belt pulley
4 Refrigerant compressor belt pulley

Introduction of the smart fortwo, Model Series 451

P13.20-2055-00

5 Crankshaft pulley
6 Tensioning device
7 Tensioning device belt pulley
8 Stretch belt

SN_Typ 451_us.book Seite 39 Freitag, 30. November 2007 1:56 13

Coolant circuit

Cooling system

In the small cooling circuit, the coolant is pumped
through the engine, the heater heat exchanger and
back to the engine via the expansion reservoir by the
coolant recirculation pump.
In the large coolant circuit, the coolant flows from the
thermostat straight to the radiator and on to the
coolant recirculation pump.
The switchover between the small and large coolant
circuit is performed by the thermostat depending on
the coolant temperature.

In the expansion reservoir the circuit is split again,
with one stream flowing direct to the coolant recircu
lation pump and the other passing through the radi
ator.

The coolant fan motor is switched on or off depending
on the engine temperature recorded by the coolant
temperature sensor and cools the coolant.

Engine M132

1 Radiator
2 Expansion reservoir
3Coolant return line
4 Coolant feed line (large circuit)
5Coolant pump
6 Coolant pump belt pulley
7Thermostat

8 Coolant feed line (small circuit)
9 Heater heat exchanger

10 Coolant pipe

B11/4 Coolant temperature sensor
M4/2 Coolant fan motor

Introduction of the smart fortwo, Model Series 451

P20.00-2339-00

39

SN_Typ 451_us.book Seite 40 Freitag, 30. November 2007 1:56 13

Cooling system

Bleeding cooling system

General

Engine M132

If some or all of the coolant has been drained, the
cooling system must be bled after refilling.

Fill

Unscrew the cooling system cap and fill the cooling
system up to the "MAX" mark in the expansion reser
voir.

i Note

The cooling system must be filled and bled only
when the engine is cold.

Bleeding

Unfasten the clamp, pull off the coolant hose and wait
until coolant emerges from the coolant hose and the
cylinder head. Then reconnect the coolant hose and
fasten it with the clamp.
Top up the expansion reservoir to the "MAX" mark
again and screw on the cooling system cap.
Warm up the engine until the thermostat opens. Switch
off the engine and check the coolant level in the
expansion reservoir.

40

1 Cooling system cap
2 Expansion reservoir

Introduction of the smart fortwo, Model Series 451

P20.00-2340-00

3 Coolant hose
4Clamp

SN_Typ 451_us.book Seite 41 Freitag, 30. November 2007 1:56 13

Engine mount/torque support

The engine with transmission is mounted on two
mounts and a torque support. They were designed to
dampen inherent engine vibrations. They also consid
erably reduce the rocking of the drive assemblies
during load changes. The reduction in vibrations and
in the tendency to rock provides a higher level of
driving safety and ride comfort.

Engine mount

Engine M132

Engine mount, transmission mount and torque support

1 Frametype integral support
2Engine mount

Introduction of the smart fortwo, Model Series 451

P22.10-2299-00

3 Transmission mount
4 Torque support

41

SN_Typ 451_us.book Seite 42 Freitag, 30. November 2007 1:56 13

Fuel supply

Fuel supply

Fuel system

A nonreturn fuel system is used for the fuel supply.
The fuel is pumped by a flow pump via the fuel filter in
the fuel tank into the fuel distributor rail according to
requirements.
Any surplus fuel is pumped via the fuel pressure
regulator straight into the buffer of the fuel pump.
The fuel pressure regulator is designed to ensure
that there is always a pressure of 46 psi (3.24 bar) at
the fuel distributor rail. The fuel tank fill level is
measured by a floatandlever sensor.

Fuel tank

The fuel tank is located in front of the rear axle under
the seats. It is made of polyethylene and is formed
such that the available installation space is used to an
optimum. The capacity of the fuel tank is 8.72 gallons
(33 liters), including a 1.32 gallon (5 liter) reserve.

The intank fuel supply system consists of a fuel pump
with fuel level sensor, fuel pressure regulator and an
integrated fuel filter.

Evaporative emission control system (purging)

The evaporative emission control system prevents
fuel vapors escaping to the atmosphere. The fuel
vapors are stored in the activated charcoal filter and
then sent later to the engine for combustion.

Leak test

The leak test for the fuel evaporation control system
must detect leaks with a diameter as of 0.02 in (0.5
mm) and must take place in three stages (function
chain):

• Test for gross leaks (equal to or greater than 0.12
in (3 mm))

• Test for fine leaks (equal to or greater than 0.04 in
(1 mm))

• Test for very fine leaks (equal to or greater than

0.02 in (0.5 mm))

Test for gross leaks

The outside air shutoff valve is closed and the tank
vent valve is opened. Intake manifold vacuum present
in fuel tank. This vacuum is measured by the tank
pressure sensor.

If no vacuum is built up in the fuel tank (approx. 0.1
psi (6 mbar) within approx. 12 seconds) there is a
major leak (e.g. tank cap open, hose line loose).
The test will be interrupted and the "gross leak" fault
will be registered.
If the MESFI [ME] control unit detects a system with
a gross leak, the fuel reserve warning lamp in the
instrument cluster flashes and the message "CHECK
FILLER CAP" appears in the multifunction display.

Test for fine leaks

The tank vent valve is closed at a vacuum of around 

0.1 psi (6 mbar). The system is closed and thereby

airproof. The vacuum is then measured for approx. 30
seconds. The vacuum must not reduce more rapidly
than 0.004 to 0.007 psi/s (0.3 to 0.5 mbar/s) (depends
on fuel level). If the vacuum drops more rapidly, there
is a fine leak.

42

The test will be interrupted and the "fine leak" fault
will be registered.

Introduction of the smart fortwo, Model Series 451

SN_Typ 451_us.book Seite 43 Freitag, 30. November 2007 1:56 13

Fuel supply

Check for very fine leaks

If no fine leak is recognized then purging is briefly
enabled and then the vacuum of about 0.1 psi (6
mbar) is built up again. The vacuum must not reduce
more rapidly than 0.0014 to 0.002 psi/s (0.1 to 0.15
mbar/s) in the closed system (depends on fuel level).

If the vacuum drops more rapidly, the fault "very fine
leak" will be registered.

The reduction in vacuum depends on the fuel level in
the fuel tank and on outgassing of the fuel. The
outgassing of the fuel is measured just before the test
by the fuel tank pressure sensor and is allowed for
during fault determination.

The test for fine and very fine leaks is aborted if an
excessive lean correction of the lambda control takes
place during the buildup of the vacuum.

The function of the tank vent valve is checked at the
same time by the actuation. If the closed tank vent
valve jams, the fault "gross leak" is stored.

Test requirements

• Engine at idle

• Vehicle stationary

• Drive position "D" or "R" is engaged

• Offperiod after engine start elapsed (approx. 16
minutes) or mixture adaptation performed

• Lambda control enabled

• Intake air temperature <113° F (<45 °C)

• Coolant temperature at engine start <212° F (<100
°C)

• Air injection not active

• Air pressure >1.12 psi (>780 hPa) (i.e. no tests
performed above approx. 2735 yd (2500 m)
altitude)

• Low loading of activated charcoal canister

• Fuel level in fuel tank between approx. ¼ and ¾

• No fault in outside air shutoff valve

• No fault in the fuel tank pressure sensor

• No fault in tank vent valve

• Battery voltage > 11 V

The outside air shutoff valve is reopened after the
tests.

Fuel system

Introduction of the smart fortwo, Model Series 451

43

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Fuel supply

Fuel system

44

Fuel system

1Fuel tank
2 Activated charcoal filter
3 Vent line
4 Filler neck
5 Filler neck hose connection
6 Purge line
7 Fuel distributor rail

Introduction of the smart fortwo, Model Series 451

P47.-10-2433-00

B4/3 Fuel tank pressure sensor
M3/3 Fuel pump with fuel level sensor
Y50 Outside air shutoff valve
Y58 Tank vent valve

SN_Typ 451_us.book Seite 45 Freitag, 30. November 2007 1:56 13

Overview

Design

The exhaust system is made of stainless steel and
consists of the following components:

•Exhaust manifold

• Catalytic converter

• Main muffler

Muffler system

When designing the muffler systems, it was important
both to minimize the exhaust back pressure and
achieve optimum acoustic tuning. The muffler system
is rigidly fixed to the vehicle body.

Exhaust aftertreatment

A control sensor and a diagnostic sensor are installed
for exhaust aftertreatment.
Aftertreatment of the exhaust gases is performed by
a catalytic converter with monolithic coating.

Exhaust system

Exhaust system

1 Exhaust manifold
2 Catalytic converter
3Main muffler

G3/1 O2 sensor downstream of TWC [KAT]
G3/2 O2 sensor upstream of TWC [KAT]

Introduction of the smart fortwo, Model Series 451

P49.00-2109-00

45

SN_Typ 451_us.book Seite 46 Freitag, 30. November 2007 1:56 13

Secondary air injection

Secondary air injection

Engine 132 is fitted with a secondary air injection
pump (electric air pump), which injects additional
fresh air in order to reduce exhaust gas emissions

Exhaust system

after a cold start and to accelerate the warming of the
catalytic converter to its reaction temperature.

The necessary air is injected into the exhaust ports in
the cylinder head by the secondary air injection pump
via the combination valve. The secondary air injection
pump is actuated by the MESFI [ME] control unit via a
relay.

The secondary air injection pump switchover valve is
supplied with vacuum from the vacuum reservoir at
the intake manifold via a check valve.

When actuated, the secondary air injection pump
switchover valve releases vacuum to the combination
valve. This opens and the air injected by the
secondary air injection pump passes through to the
exhaust ports in the cylinder head.

The injected air reacts with the hot exhaust gases in
the outlet port. The carbon monoxide (CO) and hydro
carbon (HC) are oxidized. This "afterburning"
process increases the exhaust temperature and
reduces pollutants.

The duration of secondary air injection is dependent
on the coolant temperature.
The secondary air injection pump is only actuated at a
coolant temperature of 45 °F to 97 °F (7 °C to 36 °C)
and for a maximum duration of 33 seconds.

46

Secondary air injection

1 Cylinder head
2 Combination valve
3Air hose
4Vacuum hose

Introduction of the smart fortwo, Model Series 451

P14.30-2183-00

M33 Secondary air injection pump
Y32 Secondary air injection pump switchover

valve

SN_Typ 451_us.book Seite 47 Freitag, 30. November 2007 1:56 13

5speed automated manual transmission (AMT 2)

Transmission description

The smart fortwo is fitted with the newly developed
2nd generation 5speed automated manual transmis
sion (AMT 2).

Advantages of the 5speed automated manual trans
mission:

•Greater shift comfort

• Reduced fuel consumption

Features:

• 5speed transmission

• Twodrum control

• Potentiometerfree position sensor system

• Mechanical park pawl

The driver can choose between two operating modes:

• Automatic mode (selector lever in position “D“)

• Manual mode (selector lever in position M “+/“)
with operation via the selector lever or paddle
shifts on the steering wheel (SAL)

Automated manual transmission

5speed manual transmission (AMT 2)

Introduction of the smart fortwo, Model Series 451

P26.10-2167-00

47

SN_Typ 451_us.book Seite 48 Freitag, 30. November 2007 1:56 13

Transmission description

Transmission model G 717.482

Number of forward/reverse gears 5/1

AMT 2 in model 451

Unit

Max. transferable torque lbft

Automated manual transmission

Clutch Singleplate dry clutch

Overall length (including 3 in (75 mm) for clutch) in

Housing material Aluminum alloy

Weight (without oil charge) lb

Oil charge (permanent charge) US qt

Housing Twopiece with bell housing

(Nm)

(mm)

(kg)

(l)

88

(120)

14.3

(364)

Approx. 74.9

(34)

2.4

(2.3)

48

Introduction of the smart fortwo, Model Series 451

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Shift mechanism

Shift mechanism

The central components of the shift mechanism are
two selector drums for moving the shift forks. Each
selector drum is driven by a separate electric motor
via two sintered spur gear sets. One selector drum
shifts the odd gears, while the other shifts the even
gears and reverse gear.

The position of the selector drum, and thus the
current shift position, is determined by two incre
mental sensors in each electric motor.

Both electric motors and the spur gears are located in
a common aluminum housing, the actuator unit, which
is mounted on the transmission.

The two selector drums are arranged to allow over
lapping shift operations to minimize shift times. It is
possible to skip gears (e.g. double downshifts).

Automated manual transmission

Design of shift mechanism

1 Shift fork for shift collar 5
2 Shift fork for reverse gear sliding gear
3 Shift fork for shift collar 1/3
4 Shift fork for shift collar 2/4
5 Main shaft

6 Selector drum 1/3, 5
7 Selector drum 2/4, R
8 Input shaft
M17/3 Transmission motor 1
M17/4 Transmission motor 2

Introduction of the smart fortwo, Model Series 451

P26.60-2320-00

49

SN_Typ 451_us.book Seite 50 Freitag, 30. November 2007 1:56 13

Shift mechanism

Function

The shift forks are displaced by the selector drums
parallel to the transmission shafts. They in turn slide
the shift collars on the input shaft or the main shaft
towards the respective idler gears.

The actuation of the shift forks is conducted by two
independent selector drums, each of which has a
groove. The sliding blocks for two shift forks run in
each groove.

Automated manual transmission

Shift positions

Neutral (N) and reverse gear (R)

a Selector drum 1/3, 5
b Selector drum 2/4, R
c Selector drum adjustment (1 grid square =
40°)
d Sliding block deflection (1 grid square = 0.3 in

(7.5 mm))

Neutral position (N)

Selector drum 1/3, 5:

•Sliding block of shift fork for shift collar 1/3

•Sliding block of shift fork for shift collar 5

Selector drum 2/4, R:

•Sliding block of shift fork for shift collar 2/4

•Sliding block of shift fork for sliding gear, reverse
gear

The positions of both sliding blocks in the same
groove are offset to each other by 120°. If a sliding
block displaces a shift fork from the center position,
the other sliding block is in the straight area of the
groove (in center position of respective shift fork).

Reverse gear (R)

The selector drum 2/4, R rotates through 120°
downwards. This displaces the upper sliding block
by 0.89 in (22.5 mm) to the left. The reverse gear
sliding gear engages in the outer teeth of shift
collar 1/3.

The sliding blocks in the selector drum 1/3, 5 are in
the neutral position.

The sliding blocks in the grooves of the selector
drum are in the neutral position. No gear is
engaged.

50

P26.60-2356-00

Introduction of the smart fortwo, Model Series 451

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Shift positions

Shift mechanism

1st gear (1) and 2nd gear (2)

a Selector drum 1/3, 5
b Selector drum 2/4, R
c Selector drum adjustment (1 grid square =
40°)
d Sliding block deflection (1 grid square = 0.3 in

(7.5 mm))

1st gear (1)

The selector drum 1/3, 5 rotates through 40° down
wards. This displaces the upper sliding block by 0.3
in (7.5 mm) to the left. The shift collar 1/3 is slid into
the idler gear of the first gear. The sliding blocks in
the selector drum 2/4, R are in the neutral position.

2nd gear (2)

For the change from 1st gear to 2nd gear, the two
selector drums rotate through 40° upwards. This in
turn displaces the lower sliding block in the
selector drum 2/4, R by 0.3 in (7.5 mm) to the left.
The shift collar 2/4 is slid into the idler gear of the
second gear. The sliding blocks in the selector
drum 1/3, 5 are in the neutral position.,

Automated manual transmission

Introduction of the smart fortwo, Model Series 451

P26.60-2357-00

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Shift mechanism

Shift positions

3rd gear (3) and 4th gear (4)

a Selector drum 1/3, 5
b Selector drum 2/4, R
c Selector drum adjustment (1 grid square =
40°)
d Sliding block deflection (1 grid square = 0.3 in

(7.5 mm))

3rd gear (3)

For the change from 2nd gear to 3rd gear, the two
selector drums rotate through 40° upwards. The

Automated manual transmission

upper sliding block in the selector drum 1/3, 5 is
displaced by 0.3 in (7.5 mm) to the right. It presses
the shift collar 1/3 into the idler gear of the third
gear. The other sliding blocks are in the neutral
position.

4th gear (4)

For the change from 3rd gear to 4th gear, the two
selector drums rotate through 40° upwards. The
lower sliding block in the selector drum 2/4, R is
displaced by 0.3 in (7.5 mm) to the right. It presses
the shift collar 2/4 into the idler gear of the fourth
gear. The other sliding blocks are in the neutral
position.

52

P26.60-2358-00

Introduction of the smart fortwo, Model Series 451

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Shift positions

Shift mechanism

5th gear (5)

a Selector drum 1/3, 5
b Selector drum 2/4, R
c Selector drum adjustment (1 grid square =
40°)
d Sliding block deflection (1 grid square = 0.3 in

(7.5 mm))

5th gear (5)

For the change from 4th gear to 5th gear, the
selector drum 1/3, 5 rotates through 40° upwards.
The lower sliding block in the selector drum 1/3, 5
is displaced by 0.3 in (7.5 mm) to the left. It presses
shift collar 5 into the idler gear of the fifth gear.
The selector drum 2/4, R is rotated through 40°
downwards. The sliding blocks in the selector drum
2/4, R are in the neutral position.

Automated manual transmission

Introduction of the smart fortwo, Model Series 451

P26.60-2362-00

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Synchronization

BorgWarner synchronization

All forward gears are equipped with a BorgWarner
synchronization.
Reverse gear is not synchronized.

Automated manual transmission

Function

Before the shift collar (3) positively connects the
sleeve carrier with the corresponding idler gear,
the tapered pairs of faces contact the clutch body
(1), synchronizer ring (2) and, where applicable, an
intermediate ring. The engine's gear is run at the
speed of the corresponding driveside gear; only
then do the locking splines (4) release the
remaining travel of the shift collar. The shift collar
travel from neutral to complete engagement in the
relevant idler gear is approx. 0.3 in (7.7 mm).

54

1Clutch body

P26.50-2173-00

2 Synchronizer ring
3 Shift collar
4 Locking splines

Introduction of the smart fortwo, Model Series 451

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Transmission rpm sensor (L2)

Location

The transmission rpm sensor is mounted to the
transmission housing.

Task

The rpm sensor determines the rotational speed of
the input shaft. The recorded speeds of the crank
shaft and input shaft are used to monitor the clutch
operation. The speeds of the input shaft and the
drive wheels are used to determine the actual gear
engaged.

The diagram illustrates the oscilloscope picture of
an rpm sensor.

Transmission control

Automated manual transmission

1 Input shaft
L2 Transmission rpm sensor

P26.19-2104-00

Introduction of the smart fortwo, Model Series 451

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Transmission control

Transmission motors 1 and 2 (M17/3 and M17/4)

Location

The transmission motors are located on the trans
mission housing.

Task

Depending on the shift request from the automated
manual transmission control unit (N15/6), the
transmission motors adjust the selector drums via a
twostage spur gear transmission. Actuation is
pulsewidth modulated by two output stages with

Automated manual transmission

four electronic switches each. Upon reaching the
specified position the transmission motor is
braked. It can, if necessary, be actuated with
opposing voltage, if an overshoot beyond the spec
ified position is to be prevented or reversed.

Actuation of the transmission motors is monitored
by the incremental sensors, which are located on
each motor shaft. These detect the rotation angle
and rotation direction of the respective transmis
sion motor using the integrated Hall sensors.

The transmission motors are only actuated to
execute the shift operations. Once a target position
is reached, a pin engages in the locking groove of
the selector drum to maintain the selected gear.

1 Transmission motor 1 selector drum

P26.60-2321-00

2 Transmission motor 2 selector drum
M17/3 Transmission motor 1
M17/4 Transmission motor 2

56

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Automated manual transmission control unit (N15/6)

Location

The automated manual transmission control unit is
located in the passenger compartment under the
driver seat.

General

The transmission control converts the driver's
shift requests into corresponding control signals
to the clutch and the 5speed automated manual
transmission.

Transmission control

This is done by relaying the shift signal about the
shift request at the electronic selector lever
module control unit over a direct line to the auto
mated manual transmission control unit.

The automated manual transmission control unit
checks the plausibility of the shift request in
relation to the vehicle speed, the load (acceler
ator pedal position) and the engine speed.

If the plausibility check is passed, the automated
manual transmission control unit sends the signal
to initiate the selected shift operation to the two
actuator motors for the two selector drums and to
the clutch motor to open or close the clutch.

Task

The automated manual transmission control unit
controls the following functions depending on the
input information:

• Engaging first gear at vehicle standstill

•Gear change

• Compulsory upshift just before maximum
engine speed is reached

•Compulsory downshift when engine idle speed
is approached

• Downshift for kickdown

• Disengaging the gear after 1 s when a door is
opened without the service brake or
accelerator pedal being actuated

• Crawl function

•Clutch operation

• Monitoring of clutch load

Automated manual transmission

P26.19-2145-00

N15/6 Automated manual transmission control unit

The automated manual transmission control unit
directly reads the signals from the following compo
nents:

• Transmission rpm sensor (L2)

• Transmission motor 1 (M17/3)

• Transmission motor 2 (M17/4)

• Clutch motor (M18)

• Electronic selector lever module control unit
(N15/5)

• Park pawl switch (S16/2)

Introduction of the smart fortwo, Model Series 451

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Transmission control

The following components are actuated directly by
the automated manual transmission control unit:

• Transmission motor 1 (M17/3)

• Transmission motor 2 (M17/4)

• Clutch motor (M18)

Electronic selector lever module control unit (N15/5)

Automated manual transmission

Location

The electronic selector lever module control unit is
located in the center console.

Task

The electronic selector lever module control unit
records the shift requests of the driver.

Communication via CAN takes place with the
following components:

• Instrument cluster (A1)

• MESFI [ME] control unit (N3/10)

• SAM control unit (N10/10)

• Electronic selector lever module control unit
(N15/5)

• ESP control unit (N475)

The shift positions “N”, “R”, “+” and “” are
detected by Hall sensors in the electronic selector
lever module control unit and are read and evalu
ated by the electronics in the electronic selector
lever module control unit. The signals corre
sponding to the shift lever positions are trans
ferred to the automated manual transmission
control unit.

The release button on the selector lever must be
actuated in order to move the selector lever to the
following positions:

•From P to R, N or D

•From R to P

•From N to R or P

The transmitter key can only be removed in position
0 if the selector lever is in position P.

When the transmitter key is removed, the selector
lever is locked in position P.

1 Unlock button

P26.60-2375-00

N15/5 Electronic selector lever module control unit

PPark
RReverse gear
NNeutral position
D Automatic mode
MManual mode
+Upshift
Downshift

i Note

When reverse gear is requested, the backup light
is actuated directly by the electronic selector
lever module control unit.

58

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Manual mode

In manual mode (selector lever in position M), the
gears are shifted either using the selector lever or
using the paddle shifts on the steering wheel (SAL).

The gear which is currently selected is displayed on
the multifunction display in the instrument cluster.
The gear indicator may change to provide gearshift
recommendations (arrow up or down). The gearshift
recommendations are based on a driving style
which optimizes fuel consumption.

Automatic mode

Transmission control

In automatic mode (selector lever in position D), the
automated manual transmission control unit deter
mines the gear changes. The selected gear range D
is displayed on the multifunction display in the
instrument cluster.

1 Gear range display (automatic mode)
2 Gear display (manual mode)

A1 Instrument cluster
A1p13 Multifunction display

P54.32-5683-00

Automated manual transmission

Introduction of the smart fortwo, Model Series 451

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Transmission control

Automated manual transmission

Data flow chart of transmission control

1 Circuit status
2Shift request
3 Transmission speed
4 Clutch request
5Clutch motor status
6 Gear change request
7 Transmission motor status
8 Engine speed

9 Backup light actuation
10 Vehicle speed
11 Shift program selection
12 Accelerator pedal position
13 Brake pedal status
14 Door status
15 Engaged gear
16 Gear indicator actuation
17 Park pawl status

P26.19-2141-00

A1 Instrument cluster
A45 Fanfare horns and airbag clock spring con

tact
E3e3 Left backup light
E4e3 Right backup light
L2 Transmission rpm sensor
M17/3 Transmission motor 1
M17/4 Transmission motor 2
M18 Clutch motor
N3/10 MESFI [ME] control unit (gasoline engine)
N10/10 SAM control unit
N15/5 Electronic selector lever module

control unit
N15/6 Automated manual transmission

control unit
N475 ESP control unit
S16/2 Park pawl switch
S112s1 Steering wheel gear shifter PLUS (SAL)
S112s2 Steering wheel gear shifter MINUS (SAL)

CAN Controller Area Network

(data bus/CAN bus)

60

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Mechanical park pawl

In addition to the parking brake, the 5speed auto
mated manual transmission is equipped with a
mechanical park pawl to prevent the vehicle from
rolling away. The mechanical park pawl is operated
by the electronic selector lever module control unit
via a cable.

The status of the park pawl is reported to the auto
mated manual transmission control unit via the park
pawl switch (S16/2).

Park pawl

Automated manual transmission

1 Transmission
2Cable
3Park pawl

N15/5 Electronic selector lever module control unit
S16/2 Park pawl switch

Introduction of the smart fortwo, Model Series 451

P26.60-2377-00

61

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Clutch

Singleplate dry clutch

A singleplate dry clutch, consisting of clutch plate
and pressure plate, is installed on model 451.

Automated manual transmission

An internal computer in the automated manual trans
mission control unit evaluates the clutch load. If a
threshold value is exceeded, the clutch starts to pulse
as an overload warning to the driver.
If the overloading continues, e.g. if the car is being
held with the clutch on a gradient, the clutch is closed
in order to provoke a stall.

62

Singleplate dry clutch

P25.00-2010-00

1Pressure plate
2Clutch plate
3 Flywheel with starter ring gear

Introduction of the smart fortwo, Model Series 451

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Clutch motor

Clutch

General

Model 451 is fitted with a 5speed automated manual
transmission. This means that a singleplate dry
clutch is installed instead of the torque converter that
is usual with conventional automatic transmissions.
The singleplate dry clutch is actuated by the clutch
motor.

Function

When the automated manual transmission control unit
issues a request for a gear change, the clutch motor
is actuated at the same time. The electric motor inte
grated in the clutch motor operates the clutch via the
actuating plunger. The power flow is interrupted and
the shift operation can be performed.

Automated manual transmission

4 Electric motor
5 Electric motor connector
6 Actuating plunger

M18 Clutch motor

Introduction of the smart fortwo, Model Series 451

P25.19-2010-00

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Front axle

Chassis

Front axle

The front axle has a classic McPherson design.

The supporting ball joint is pressfitted with the
transverse control arm forming a single component
unit. If repairs are necessary, the supporting ball
joint must be replaced complete with the cross
member since a satisfactory pressfit cannot be
guaranteed in the repair shop.

The wheel bearing in the steering knuckle is not
available separately either because it is pressed into
the steering knuckle and can only be ordered as a
complete unit with the steering knuckle.

Adjustment capabilities

On the front axle it is only possible to adjust the toe;
the camber can only be corrected by utilizing the
"play" at the attachment points of the front axle.

64

Front axle  smart fortwo model 451

1 Front axle crossmember
2Stabilizer bar
3 Transverse control arm with pressfitted support

ing ball joint

Introduction of the smart fortwo, Model Series 451

P33.00-2086-00

4Coil spring
5 Twotube shock absorber
6 Wheel carrier, cast iron

with pressedin wheel bearing

SN_Typ 451_us.book Seite 65 Freitag, 30. November 2007 1:56 13

Rear axle

Rear axle with suspension

The rear axle consists of:

•Axle tube

• Frametype integral support

•Coil springs

• Bar link

• Singletube shock absorbers

• Center bearing

Chassis

The frametype integral support supports the rear
wheel drive module. The coil springs are located at the
outsides and support the body against rolling move
ments.

The singletube shock absorbers are fixed in place at
the top with pin bearings.

Rear axle  smart fortwo model 451

7Axle tube
8 Frametype integral support
9Coil spring

10 Bar link

11 Singletube shock absorber pin bearing
12 Singletube shock absorber
13 Center bearing

Introduction of the smart fortwo, Model Series 451

P35.00-2075-00

65

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Rear module

Chassis

Lowering the rear module

On model 451, the rear wheel drive module can be
lowered.

This shortens removal/installation time for various
major assemblies such as the refrigerant compressor,
starter, alternator etc., because all the attached
parts on the engine and the engine itself can be
reached very quickly and with relatively little effort.
This shortens repair times and reduces costs while
improving customer satisfaction at the same time.

66

Lowered rear drive module

P35.00-2085-00

Introduction of the smart fortwo, Model Series 451

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Tire pressure monitor

General

The tire pressure monitoring system (TPM [RDK])
monitors the air pressure in the individual tires and
improves active safety. A previously stored tire pres
sure is used as a comparative value. If a relevant loss
of pressure occurs, the tire pressure monitor
warning lamp in the instrument cluster warns the
driver. The tire pressure measuring range is p = 0 to
78 psi (p = 0 to 5.5 bar).

The TPM [RDK] system has the following subfunctions:

• Tire pressure sensing

• Warning display

• Manual restart

Function requirements

• Circuit 15 ON

• Tire pressure monitor (TPM [RDK]) system
functional

Tire pressure sensing

The TPM [RDK] control unit is permanently opera
tional. Each time the CAN wakes up, the control unit
performs a reinitialization. While driving, the tire
pressure monitoring (TPM [RDK]) system continuously
monitors the tire pressure of all rotating wheels (with
circuit 15 OFF for a further t = 19 min). When the
vehicle is parked for t > 19 min, onboard wheel
detection and axle assignment must first be
completed via the TPM [RDK] wheel sensors. While
driving, the TPM [RDK] wheel sensors transmit data
telegrams every 60 seconds.

These data telegrams contain the following informa
tion:

• Tire pressure

• Tire air temperature

• Individual serial number

• Status information
(manufacturer, direction of rotation, operating
mode etc.)

Chassis

In addition the TPM [RDK] control unit takes into
account the outside temperature and the vehicle
speed for the tire pressure determination. These data
are provided via CAN by the instrument cluster.

Warning indicator

A warning is issued when a relevant loss of pressure
has been detected in at least one of the tires. The
warning is issued in the instrument cluster via the tire
pressure monitor warning lamp, but the specific tire
where pressure loss has occurred is not specified.

Manual restart

The tire pressure to be monitored can be reset via the
TPM [RDK] switch on the cockpit switch panel. When
the TPM [RDK] switch is pressed, the current tire
pressure is stored in the memory of the TPM [RDK]
control unit and is then used as the reference pres
sure, as long as it is within the permissible limits.

The tire pressure monitor warning lamp in the instru
ment cluster flashes to indicate that a manual restart
has taken place.

i Note

A manual restart must be performed each time the
tire inflation pressure is changed and when a
wheel, wheel sensor or the TPM [RDK] control unit
is replaced.
If the nut on the valve element of a wheel sensor is
loosened, all components of the valve element
must be replaced.

See the Workshop Information System (WIS) for
further instructions and information.

Introduction of the smart fortwo, Model Series 451

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Tire pressure monitor

Chassis

Location of TPM [RDK] components

A1 Instrument cluster
A1e66 Tire pressure monitor warning lamp
A69/1 Left front TPM [RDK] wheel sensor
A69/2 Right front TPM [RDK] wheel sensor
A69/3 Left rear TPM [RDK] wheel sensor
A69/4 Right rear TPM [RDK] wheel sensor

P40.15-2424-00

B14 Outside temperature display temperature

sensor
N10/10 SAM control unit
N88 TPM [RDK] control unit
S6/1 Cockpit switch group
S6/1s9 TPM [RDK] switch

68

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Brakes

Task

The task of the brake system is to brake the vehicle or
hold it at a standstill.
The system includes the service brake, which brakes
the vehicle while it is being driven, and the parking
brake, which secures the vehicle when it is at a stand
still.

Components of the parking brake

• Hand brake lever with hand brake cables

• Parking brake mechanism integrated into rear
drum brake

Function of parking brake

When the handbrake lever is actuated, a relay lever is
actuated at the rear brake shoes of the left and right
drum brakes via the handbrake cables. This presses
the brake shoes of the drum brakes against the
insides of the brake drums to build up the required
brake force.

Chassis

Components of the service brake

• Disk brakes with brake calipers on front axle

• Drum brakes with aluminum wheel brake cylinders
on rear axle

• Brake fluid reservoir

• Brake lines and brake hoses

• Brake pedal module

• ESP unit, consisting of ESP control unit and ESP
hydraulic unit

Function of service brake

The service brake is a hydraulic 2circuit brake
system with TT (front/rear) split.

The force applied to the brake pedal is transferred to
the brake booster via a linkage. The brake booster
multiplies this forces and uses it to pressurize the
master brake cylinder. The brake pressure is built up
via the master brake cylinder.
The brake force is distributed to the disk brakes and
drum brakes by the ESP unit via the integrated
antilock brake system (ABS) and the electronic brake
force distribution (EBD) system.

Introduction of the smart fortwo, Model Series 451

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Brakes

Chassis

70

Brake system

1 Brake pedal module
2 Brake disk
3 Brake caliper
4 Expansion reservoir
5ESP unit
6 Hand brake cables
7 Drum brake (consisting of: anchor plate, wheel

brake cylinder, brake shoe, springs and brake
drum)

8 Hand brake lever

Introduction of the smart fortwo, Model Series 451

P40.10-2711-00

B24/15 Yaw rate, lateral and longitudinal accelera

tion sensor
L6/1 Left front rpm sensor
L6/2 Right front rpm sensor
L6/3 Left rear rpm sensor
L6/4 Right rear rpm sensor
N475 ESP control unit
N49 Steering angle sensor

SN_Typ 451_us.book Seite 71 Freitag, 30. November 2007 1:56 13

Brakes

Brake pedal module

The brake pedal module is located on the underfloor
and consists of the following assemblies:

•Pedals

•Carrier

•Brake booster

• Master brake cylinder

Chassis

Pedals

The pedals consist of:

• Pedal head

•Perforated boot

• Pedal assembly seal

•Housing

•Linkage rod

• Brake pedal module cover

• Seal for brake pedal module cover

•Brake light switch

Brake pedal module

9 Pedal head
10 Housing
11 Carrier
12 Brake booster
13 Master brake cylinder
14 Grommet
15 Brake pedal module cover

16 Linkage
17 Seal
18 Pedal assembly seal
19 Perforated boot
20 Bolt

S9/1 Brake light switch

Introduction of the smart fortwo, Model Series 451

P42.10-2712-00

71

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Brakes

Chassis

Pedals

The seals and the boot on the pedals may not be
damaged otherwise moisture can penetrate into the
interior compartment.
To ensure that the pedals remain leaktight, the brake
pedal module cover must be replaced each time the
pedals are disassembled.

Brake light switch

The brake light switch in the pedal assembly is only
accessible after the brake pedal module cover has
been removed.
The brake light switch is actuated via the linkage in
the pedal assembly when the brake is actuated. The
signal from the brake light switch is read by the ESP
control unit.
The free travel of the brake light switch must be
correctly adjusted to ensure that the brake light
switch operates properly.

Brake lines

Brake system bleeding

Whereas the brake fluid can be replaced by one
person, the hydraulic brake system can only be bled
by two people working together. When bleeding the
primary and secondary circuit, one person must build
up the pressure required by the brake fluid changer
by repeatedly actuating the brake pedal. The second
person is needed to:

• Actuate the ESP hydraulic unit via diagnosis at the
same time and perform the bleeding procedure
when bleeding the primary circuit

• Perform the bleeding procedure when bleeding the
secondary circuit

i Note

To ensure that the brake system is not damaged,
the filling pressure on the brake fluid changer
may be set to max. 2.8 psi (2 bar).

All brake lines may only be retightened twice at the
most when work is performed on the vehicle. If a
threaded connection on a brake line is loosened and
then retightened, this must be documented. The
respective threaded connection must be marked in
color with a suitable safety paint.

The following color codings are specified:

• First retightening: yellow marking

• Second retightening: red marking

If the respective threaded connection is loosened
again after being retightened for a second time, the
detached brake line must be replaced. This also
applies if it is not possible to trace how often the
threaded connection has previously been loosened.

Basic adjustment of brake shoes

After brake shoes are replaced or removed/installed,
basic adjustment of the drum brake must be
performed. To do so, the brake shoes are measured
and adjusted using the slack adjuster.

Drum brake adjustment

Manual adjustment of the clearance between brake
shoe and brake drum is not permissible. Adjustment
may only be performed via the automatic slack
adjuster of the brake shoes to prevent grinding or
locking of the drum brake.

i Note

See the Workshop Information System (WIS) for the
exact procedure for repairing the brake system
and for the relevant safety information.

72

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Brakes

ESP system

The latest ESP system (version 8.1) is installed next to
the brake pedal module on the underfloor and
features the following functions:

•ABS

•ASR

•HBA

•EBD

•ESP

•EBR

• Startoff assist

Antilock brake system (ABS)

Prevents individual wheels from locking up by regu
lating the brake pressure at the relevant wheel
brakes. The vehicle remains steerable, enabling the
driver to take evasive action himself to avoid sudden
obstacles during emergency braking.

Acceleration skid control (ASR)

Prevents the drive wheels from spinning by inter
vening in the engine management and brake pressure
regulation. ASR provides good traction and improves
vehicle stability and steerability when moving off and
accelerating.

Hydraulic brake assist (HBA)

Regulates the pressure buildup in the brake system in
relation to the vehicle speed and the actuation speed
of the brake pedal. When emergency braking is
detected by means of characteristics defined before
hand, the ESP control unit actuates the return flow
pump that is integrated in the hydraulic unit. The
maximum brake pressure is built up.

Chassis

Electronic stability program (ESP)

Minimizes oversteer or understeer by means of
specific intervention by the brake system at each
wheel on the front and rear axles. There may also be
intervention in the engine and transmission control
systems if necessary.

Engine braking regulation (EBR)

Reduces slip of the drive wheels in deceleration mode
and thereby improves directional stability and road
adhesion.

Startoff assist

Maintains the brake pressure for approx. 0.7 s after
the brake pedal is released to facilitate startoff on
uphill slopes.

Rpm sensors

The rpm sensors are active sensors, i.e. they must be
connected to a voltage source in order to operate.
They deliver a signal with an rpmindependent,
constant amplitude, and utilize the Hall effect to
detect the rpm signal.

Yaw rate, lateral and longitudinal acceleration sensor

The yaw rate, lateral and longitudinal acceleration
sensor is a combined sensor of micromechanical
design. It registers the yaw rate (yaw angle velocity)
of the vehicle about the vertical axis, the longitudinal
acceleration and the lateral acceleration.

Electronic brake force distribution (EBD)

Regulates the brake pressure at the rear wheels in
the partial braking range in order to improve the
stability of the vehicle and the braking effect.

Introduction of the smart fortwo, Model Series 451

i Note

In the event of an emergency stop in which the
vehicle is braked to a standstill from a speed in
excess of 43 mph (70 km/h), the SAM control unit
automatically activates the hazard warning
system. Deactivation of the hazard warning func
tion occurs automatically when the vehicle speed
is detected to have risen above 6 mph (10 km/h) or
manually by actuation of the hazard warning
system switch.

73

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Brakes

Chassis

Data flow chart of Electronic Stability Program ESP

1 ESP/ABS/ASR status
2 ESP/ABS/ASR display status
3 Wheel speed signal
4 Steering angle
5 Steering rate
6 Lateral and longitudinal acceleration
7Yaw rate
8 Engine torque control

9 Transmission control intervention
10 Brake pedal status
11 Emergency stop reference speed
12 Driver door closed status
13 Handbrake status
14 Brake fluid status

A1 Instrument cluster
A1e41 ESP warning lamp

P42.45-2662-00

B24/15 Yaw rate, lateral and longitudinal accelera

tion sensor
L6/1 Left front rpm sensor
L6/2 Right front rpm sensor
L6/3 Left rear rpm sensor
L6/4 Right rear rpm sensor
N3/10 MESFI [ME] control unit
N10/10 SAM control unit
N15/6 Automated manual transmission

control unit
N475 ESP control unit
N49 Steering angle sensor
S9/1 Brake light switch
S11 Brake fluid indicator switch
S12 Parking brake indicator switch

CAN Controller Area Network

(data bus/CAN bus)

74

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Steering

Rackandpinion steering

The smart fortwo features rackandpinion steering
as standard. The steering ratio is 22:1.

Electric power steering EPS (special equipment)

Electric Power Steering (EPS) is available as special
equipment. The steering ratio is 21:1.

The tasks of the EPS system are as follows:

• Power assistance with Servotronic

• Adaptation of the steering forces

• Active steering centering

General

Electric Power Steering (EPS) is a direct steering
system with integral speeddependent power assis
tance and active steering centering. This ensures
that steering wheel forces remain low when the
vehicle is being maneuvered.
An electromechanical system offers the following
advantages compared to a conventional hydraulic
power steering system:

• Less weight and smaller installation space

• Greater degree of freedom to adjust the steering
assistance

• Reduced fuel consumption.

EPS operates without hydraulic components such as
pumps, reservoirs, coolers, lines and hydraulic fluid,
and is therefore a dry, environmentally compatible
system.

Chassis

Electric power steering EPS

Introduction of the smart fortwo, Model Series 451

P46.10-2935-00

75

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Steering

Chassis

Design

The main components of the electric power steering
(EPS) system are the power steering motor, a DC
brushtype electric motor with maximum 35 Ampere
power consumption and the power steering control
unit.

The power steering control unit communicates via the
CAN data bus and is located in the vehicle interior on
the left of the firewall.

The rackandpinion mechanical components for the
electric power steering (EPS) are accommodated in a
steering housing made of diecast aluminum, to which
the power steering motor is also flangemounted.

To provide steering assistance, the steering gear
pinion shaft transmits the rotational movement of the
steering gear input shaft to the teeth of the toothed
rack. The power steering motor transmits force for
steering assistance to the spur toothing of the hyper
bolic gear via a worm shaft. The hyperbolic gear is
fixed to the pinion of the steering gear pinion shaft.
The power steering torque sensor is located in the
steering gear housing between the steering gear
input shaft and hyperbolic gear.

76

P46.10-2933-00

Components of the electric power steering (EPS)

1 Steering gear housing
2 Steering gear pinion shaft
3 Steering gear input shaft
4Toothed rack
5Worm shaft
6Hyperbolic gear

B23 Power steering torque sensor
M19 Power steering motor
N68 Steering assist control unit

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Steering

Function

Function requirement

Steering assistance is activated after engine start
and at a minimum engine speed of 500 rpm.

Steering power assistance

As the driver turns the steering wheel, a steering
torque is produced at the drag link which is regis
tered by the power steering torque sensor and
forwarded to the power steering control unit.

The steering torque is used as an actuating variable
for the electric assistance force. It is derived from
the rotation of the torsion bar, which is located
between the steering gear input shaft and steering
gear pinion shaft on the same axis.
The power steering torque sensor is located around
the torsion bar. This determines the torque over a
range of +/ 8.1 lbft (11 Nm) and at a resolution of

0.037 lbft (0.05 Nm).

Chassis

P46.10-2934-00

Steering torque of the electric power steering (EPS)

The power steering control unit uses the steering
torque measurement to determine the level of torque
that needs to be provided to supplement the steering
force.
Based on this information and depending on the
vehicle speed signal from the ESP control unit and the
engine speed signal from the MESFI [ME] control
unit, the power steering control unit determines the
current requirement of the power steering motor as
per the programmed characteristic field.

The power steering motor transmits the appropriate
supplementary steering torque to the face of the
hyperbolic gear via the worm shaft.

2 Steering gear pinion shaft
3 Steering gear input shaft
5Worm shaft
6 Hyperbolic gear
7Torsion bar

B23 Power steering torque sensor
M19 Power steering motor
N68 Steering assist control unit

Introduction of the smart fortwo, Model Series 451

77

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Steering

Chassis

Steering centering

This function returns the steering to the center posi
tion once the driver stops applying steering torque.
The power steering motor is actuated accordingly by
the power steering control unit.

"Active center feeling" function

When the steering wheel is registered in the center
position and there are no steering movements, the
power steering motor is energized by the steering
assist control unit so that a sufficient torque is
produced to hold the steering in the straightahead
position. This actuation conveys an improved steering
center feel to the driver. The system is continuously
calibrated and learns the center position automati
cally. The longterm calibration is performed via the
ESP wheel sensor system.

Limphome function

The steering assist control unit constantly checks all
the input signals for plausibility. In the case of a faulty
component the steering, power assistance is shut
down and a fault is stored in the steering assist
control unit. The steering then continues to function
as a conventional rackandpinion steering.

i Note

If the electric steering suffers a function failure,
the electric steering indicator lamp in the instru
ment cluster lights up to indicate this.

To comply with EMC requirements, the energy line
from the power steering control unit to the power
steering motor is 85 % shielded against external influ
ences.

The power steering control unit is a CAN bus
subscriber in the overall network. The vehicle speed,
the steering angle and other data are read in over
CAN.

78

i Note

The steering power assistance is at a maximum at
low speeds and when the vehicle is stationary and
decreases as the vehicle speed increases.
Once the vehicle stops and the engine is switched
off, the steering power assistance is deactivated
in stages after approx. 3 s.

Introduction of the smart fortwo, Model Series 451

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Steering

Chassis

Data flow chart of electric power steering EPS

1 Vehicle speed
2Steering torque
3 Warning and fault message output
4 Power steering motor actuation
5 Steering angle, steering rate
6 Engine speed

A1 Instrument cluster
A1e18 Electric steering indicator lamp
B23 Power steering torque sensor
M19 Power steering motor
N3/10 MESFI [ME] control unit
N475 ESP control unit
N49 Steering angle sensor
N68 Steering assist control unit

CAN Controller Area Network

(data bus/CAN bus)

P46.35-2034-00

Introduction of the smart fortwo, Model Series 451

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Steering

Chassis

Steering wheel

Two steering wheel variants are available for model
series 451.

Variants

• Leather twospoke steering wheel of dia. 14.6 in
(370 mm) as standard equipment on the pure

• Threespoke sport steering wheel with integrated
paddle shift of dia. 13.8 in (350 mm) as standard
equipment on the passion

Paddle shifts on steering wheel

In vehicles that are fitted with a threespoke sport
steering wheel, the paddle shifts on each side of the
steering wheel can be used to shift up and down
through the gears. It is therefore possible to select a
gear on the steering wheel as well as via the gear
selector lever.
The lefthand paddle shift is used to downshift and the
righthand paddle shift is for upshifts.
The gear which is currently engaged is displayed on
the multifunction display in the instrument cluster.

Twospoke steering wheel

P46.10-2839-00

80

Threespoke sport steering wheel with paddle shifts

P46.10-2840-00

Introduction of the smart fortwo, Model Series 451

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Steering

Steering wheel removal and installation

The following components of the steering wheel are
replaceable:

• Contact unit with steering angle sensor

•Airbag module

• Paddle shifts (threespoke sport steering wheel
only)

The steering wheel must be detached first before
replacing or removing/installing any of the above
components.

Care mus t be tak en to ens ure that the front wheels are
in the straightahead position, the battery is discon
nected and the handbrake is applied before the
steering wheel is removed.

The exact procedure for removal/installation of the
steering wheel and its components is described in the
Workshop Information System (WIS).

Chassis

i Note

All control units must be deenergized before the
steering wheel is removed. For this reason, at
least 15 minutes must elapse after the battery is
disconnected before it is removed.

i Note

Care must be taken to ensure that the turn signal
is not set when removing/installing the steering
wheel otherwise the trigger tab may be damaged.

P46.10-2841-00

Introduction of the smart fortwo, Model Series 451

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Interior

Body

Interior design

The interior compartment has a classic look while still
displaying modern, typical smart features. This well
balanced overall concept helps the smart fortwo
create an exclusive overall impression with high
perceived quality.

This is helped by the lines of the instrument panel, the
door linings and the seats shaped to match. The
harmonized color scheme of the interior also gives a
positive impression in combination with the passenger
compartment as a whole.

82

Shown on the smart coupé pure

P68.00-5039-00

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Instrument panel

Interior

Body

For the design of the instrument panel, particular
emphasis was placed on the following criteria:

• Ergonomics

• Clear layout

• Passenger safety

The instrument panel is designed with straight lines
and equipped with airbags and a full length knee
bolster to improve passenger protection.

Two additional instruments (tachometer and clock)
are available as special equipment (SA) and are posi
tioned above the center console. The air vents on the
instrument panel have a cylindrical shape.

Shown on the smart coupé passion

P68.10-3852-00

Introduction of the smart fortwo, Model Series 451

83

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Interior

Body

Instrument cluster

In the center of the instrument cluster is the speed
ometer scale with the multifunction display under
neath.
On each side is a strip with indicators and warning
displays, as well as the control buttons for the multi
function display.

The task of the instrument cluster is to provide the
driver with information about the various operating
states and to provide acoustic or visual warnings in
the event of critical operating conditions. It is the
display unit for the vehicle speed and for other
systems. In addition, the instrument cluster computes
the maintenance intervals and shows them in the
multifunction display.

The instrument cluster is a device on the data
bus/CAN bus in the overall network. Most of the
signals are transmitted or received over CAN. The
following signals are supplied to the instrument
cluster over direct lines:

• Signal from outside temperature indicator
temperature sensor

• Signal from "Fanfare horns and airbag clock spring
contact“ (only on variant with SAL).

The vehicle speed is displayed by an electronic
speedometer that is driven by a stepper motor. The
ESP control unit reads the information for the speed
display from the wheel speed sensors in the form of
signals, and forwards it over CAN to the instrument
cluster. The instrument cluster processes the
incoming signals and uses them to calculate the
vehicle speed and distance traveled.

Multifunction display

The task of the multifunction display is to provide the
driver with information about variable changes in the
vehicle, the ambient conditions and the road.

The variable displays include:

• Outside temperature

• Main odometer

• Trip odometer

• Gear indicator (in manual mode)

• Automatic transmission indicator (in automatic
mode)

• Fuel reserve indicator (US gal)

• Maintenance interval display with symbol

• Fuel level and reserve indicator

•Clock

Multifunction display

P54.32-5677-00

84

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Interior

Body

Instrument cluster

1 Left button, select multiple display / set

clock

2 Right button, instrument illumination / set

clock

A1 Instrument cluster
A1e1 Left turn signal indicator lamp
A1e2 Right turn signal indicator lamp
A1e3 High beam indicator lamp
A1e5 Alternator charge monitoring and warning

lamp

A1e7 Brake fluid and parking brake warning lamp

P54.30-9683-00

A1e9 Seat belt warning lamp
A1e15 Airbag indicator and warning lamp
A1e17 ABS indicator lamp
A1e18 Electric steering indicator lamp
A1e26 CHECK ENGINE indicator lamp
A1e30 Oil pressure warning lamp
A1e41 ESP warning lamp
A1e54 Coolant temperature warning lamp
A1e66 Tire pressure monitor warning lamp
A1e67 Low beam indicator lamp
A1p8 Electronic speedometer
A1p13 Multifunction display

Introduction of the smart fortwo, Model Series 451

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Doors/flaps

Body

Side doors

The doors of the new smart fortwo follow the typical
smart brand construction principle with a metal
carrier part and the plastic CBS door paneling. The
doors of the smart coupé and the smart cabrio are
identical.

The triangular windows located above each door
handle are stationary windows held in place by bolts.

Crash requirements

The door support structure in model 451 is made of
steel. In addition, panels and sections of high
strength steel are used at strategically important
points. This is the case, for example, with the diagonal
struts and the side window slot frames.

In combination with the cockpit crossmember, this
makes the passenger compartment highly resistant to
side impacts in this section of the vehicle.

Door structure

P72.00-2185-00

1 Door carrier module
2 Diagonal strut
3 Side window slot frame
4 Cockpit crossmember

86

Emergency opening

Normally, the smart fortwo is opened from outside via
the standardequipment central locking system using
the transmitter key.
If the battery in the transmitter key cannot supply
enough power, a lock cylinder installed behind a small
cover under the handle of the left door can be used to
open the driver door manually in an emergency.

P80.20-3225-00

1 Lock cylinder for emergency opening

Introduction of the smart fortwo, Model Series 451

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Doors/flaps

Body

Design of driver door with power window and electric outside mirror

1 Door carrier module
2 Window lifter mechanism
3 Diagonal strut
4 Top door hinge assembly
5 Bottom door hinge assembly
6 Inner door lining
7 CBS door paneling
8Curved handle
9 Side window

10 Triangular window

H4/9 Left front speaker
M10/3 Left power window motor
M14/6 Left door CL [ZV] motor
M14/6s1 Left door CL [ZV] microswitch
M21/1 Left electrically adjustable and heated out

S21/1 Left power window switch
S21/2 Right power window switch
S50 Outside mirror adjustment switch
S87/7 Left door rotary tumbler microswitch

Introduction of the smart fortwo, Model Series 451

P72.10-3403-00

side mirror

87

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Doors/flaps

Body

Rearend door

88

Design of rearend door shown on the smart fortwo coupé

1 Upper rearend door
2 Upper rearend door paneling
3 Rear spoiler
4 Upper rearend door hinges
5Gasoperated strut
6Rear window
7 CBS rearend door paneling
8Lower rearend door
9 Right door lock of lower rearend door

10 Left door lock of lower rearend door

Introduction of the smart fortwo, Model Series 451

P72.20-2599-00

11 Door lock of upper rearend door
12 Door panel lining
13 Lower rearend door hinges
14 Seal

E21 Center highmounted brake lamp
M6/4 Rearend door wiper motor
S88/9 Rearend door handle switch

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Doors/flaps

Emergency unlocking of rearend door

The rearend door in the smart fortwo can be unlocked from the inside in an emergency, if the trunk lid central
locking motor for operating the rotary tumbler is defective or deenergized.

Body

Emergency unlocking in smart fortwo coupé

To do this, a small tab at the side of the trunk lid lock
paneling must be carefully bent over or broken off to
produce a small hole.

A shopmade wire must then be inserted through the
small hole so that enough downward pressure is
exerted on the relay lever in the door lock to unlock
the rearend door at the top.

A description of the procedure for manufacturing the
emergency release wire in the workshop is given in
the Workshop Information System (WIS).

Emergency unlocking in smart fortwo cabrio

In order to open the two door locks in the cabrio, a
hole must be accurately marked on the inside of the
rearend door on each side. Then a hole of 0.2 in (5
mm) diameter is drilled through the paneling on each
side of the rearend door..

A suitable screwdriver is inserted into each hole and
the rearend door is unlocked by moving the screw
driver handles simultaneously in the directions of the
arrows.

The exact dimensions for the holes and a detailed
description of the procedure can be found in the
Workshop Information System (WIS).

A Actuation direction

1 Tab/paneling hole on trunk lid lock
2 Emergency release wire

P72.20-2583-00

B Actuation direction

3 Hole (0.2 in (5 mm))
4 Screwdriver

Introduction of the smart fortwo, Model Series 451

P72.20-2582-00

89

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Roof systems

Body

Variants of roof system

Two roof variants are available for the model series
451 coupé. A fully electric Tritop fabric soft top is
installed in the cabrio.

smart fortwo coupé

• Full roof made of glass fiber reinforced
polyurethane (PU)

• Panoramic sunroof made of polycarbonate (PC)

smart fortwo cabrio

• Fully electric Tritop fabric soft top

Vehicle with PU roof

Vehicle with panoramic sunroof

P65.00-2119-00

P77.21-2226-00

90

Vehicle with fully electric Tritop fabric soft top

P77.00-2338-00

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Hard roofs on smart fortwo coupé

Full roof

In the standard equipment pure version the smart
fortwo coupé is supplied with the polyurethane (PU)
full roof. The PU roof is only available in pitted matt
black.

The PU full roof sits on the body and is bonded to the
bodyshell structure.

Panoramic sunroof

Roof systems

Body

A polycarbonate (PC) panoramic sunroof with step
lessly variable roller sun blind is available for some
equipment variants.

The roof module is bonded to the tridion safety cell.
The latest in plastics technology makes it possible to
use breakproof material extensively in the vehicle.

The material is covered with a scratchresistant
coating and the light transmission of the tint is
approx. 13 %. The material also provides 100 %
protection against UV light.

The steplessly adjustable inside roller blind can be
used to block out the sun. The roller sun blind is made
of a polyester fabric and covers the entire trans
parent area of the panoramic sunroof. The roof and
roller blind can be replaced separately.

The panoramic sunroof is manufactured by a two
component injection molding process in which the
second component material serves to blacken the
edges.

Panoramic sunroof with roller sun blind

P77.21-2225-00

Introduction of the smart fortwo, Model Series 451

91

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Roof systems

Body

Tritop fabric soft top

The Tritop fabric soft top of the smart fortwo cabrio
is the only one in the world that can be opened and
closed while driving up to the maximum speed. The
name TRITOP comes from the three main components
of the soft top:

• Folding top open

• Rear soft top stowed

• Side supports removed

The soft top control system is fully electronic and
features the following functions:

• Opening the folding top

• Closing the folding top

• Lowering the rear soft top

• Raising the rear soft top

92

Components of Tritop textile soft top

1 Folding top
2Rear soft top

Introduction of the smart fortwo, Model Series 451

P77.30-2390-00

3 Left and right side supports

SN_Typ 451_us.book Seite 93 Freitag, 30. November 2007 1:56 13

Soft top operation

The folding top and rear soft top are opened and
closed using the power soft top switch on the elec
tronic selector lever module control unit.
The folding top can also be opened remotely and auto
matically by means of a button on the transmitter key.

To operate the soft top via the power soft top switch
the vehicle's ignition must be switched on.
A short press of the power soft top switch in the
"Open" direction causes the folding top to open all the
way to its end position.
The folding top must always be fully opened before the
rear soft top can be opened. If the power soft top
switch is then pressed again and held in the "Open"
direction, the rear soft top is folded away for as long
as the switch is actuated. As soon as the rear soft top
has been stowed in its end position, its motors cut out
and the switch can be released.

Roof systems

Body

P80.35-2333-00

3 Folding top automatic open button

A Transmitter key

To close the soft top, the power soft top switch is
pressed and held in the "Close" direction until the
rear soft top has reached its upper end position and
the motors of the rear soft top cut out; the switch can
then be released.
If the power soft top switch is pressed and held again,
the folding top closes until it reaches its own end
position and the motor cuts out; then the switch can be
released again.
The rear soft top and folding top lock automatically as
soon as they reach their end positions.

i Note

For safety reasons, it is not possible to close the
folding top automatically. There would be a risk of
injury during the closing process because limbs of
vehicle occupants could become trapped between
the roof frame and folding top in the area of the
windshield.

S84 Power soft top switch

P77.00-2332-00

Introduction of the smart fortwo, Model Series 451

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Roof systems

Body

Targa roof position

Soft top control

In the targa roof position, the folding top is fully
opened, the side supports are removed and the rear
soft top is closed.

The targa roof position is important with regard to the
operation of the folding top because the side
supports must be inserted before the folding top can
be closed. The side supports are detected by a
mechanical catch in the roof cassette lock.

The central controller unit of the soft top is the SAM
control unit.

The SAM control unit reads in the actuation request
from the power soft top switch and actuates the
appropriate motors depending on the position and
status of the soft top.

The soft top is powered by a total of three motors. A
central motor in the roof cassette is responsible for
opening and closing the folding top. The folding and
raising of the rear soft top is carried out by two
motors in the left and right main bearings of the soft
top.

The soft top also incorporates the center high
mounted brake lamp and a glass rear window with an
integral rear window heater, which is also activated by
the SAM control unit.

Function sequence of soft top actuation

Function requirements:

• Switch circuit 15 ON

Pressing the power soft top switch sends a direct
signal to open or close to the SAM control unit. The
SAM control unit reads in the signal, checks whether
the function requirements are satisfied and deter
mines the status of the soft top via the microswitches
installed on the soft top. If all the preconditions are
met, the SAM control unit actuates the appropriate
motor(s) for the desired operation.

94

Targa roof position

P77.00-2340-00

Introduction of the smart fortwo, Model Series 451

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Roof systems

Body

Data flow chart of soft top control

1 Circuit 15 ON
2 Request to open folding top
3 Request to open rear soft top
4 Request to close rear soft top
5 Request to close folding top
6 Status of soft top
7 Status of roof cassette latch
8 Status of rear soft top
9 Vehicle speed

A1 Instrument cluster
K66/1 Open soft top relay
K66/2 Close soft top relay
M12/6 Electric soft top motor
M12/7 Left soft top drive
M12/8 Right soft top drive
N10/10 SAM control unit
S2/1 Ignition/starter switch
S84 Power soft top switch
S84/37 Folding top microswitch
S84/38 Left roof cassette microswitch
S84/39 Right rear soft top microswitch
S84/40 Right roof cassette microswitch
S84/41 Left rear soft top microswitch

A Transmitter key
CAN Controller Area Network

(data bus/CAN bus)

P77.39-2210-00

Introduction of the smart fortwo, Model Series 451

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Central locking

Body

Central locking (CL [ZV])

The central locking in the smart fortwo includes the
locking and unlocking of both doors and the fuel filler
flap, and the opening of the rearend door in the
smart coupé or the opening of the soft top on the
smart cabrio. A distinction is drawn between manual
and automatic functions.

Manual functions:

• Remote control with the transmitter key

• Door opening from the inside

• Operation via the interior CL [ZV] locking and
unlocking switches in the cockpit switch group

• Manual unlocking with the transmitter key at the
driverside door lock

Automatic functions:

• Speeddependent locking

• Emergency opening after crash detection

•Relocking

Unlocking or locking via the transmitter key

When the Unlock or Lock button on the transmitter key
is pressed, it sends a radio signal to the SAM control
unit. The SAM control unit checks the access authori
zation of the transmitter key. If the access authoriza
tion is valid, it actuates the following motors directly
to unlock or lock the vehicle:

Selective unlocking

If the Unlock button on the transmitter key is pressed
once, only the driver door and fuel filler flap are
unlocked. The antitheft alarm system is deactivated
and all turn signal indicators flash once.

Global unlocking

If the Unlock button on the transmitter key is pressed
again, the passenger door is unlocked and the rear
end door handle switch is enabled. The turn signal
indicators flash again once.

Door opening from the inside

The vehicle doors can always be opened from the
inside with the door handle regardless of the status of
the central locking. In this case, only the respective
vehicle door and the fuel filler flap are unlocked.

96

• Right door CL [ZV] motor

• Left door CL [ZV] motor

• Fuel filler flap CL [ZV] motor

When the vehicle is globally unlocked, the rearend
door handle switch is enabled; and when the vehicle is
locked, it is disabled.
If the rearend door handle switch is actuated when
the central locking has been globally unlocked, the
SAM control unit directly actuates the trunk lid CL
[ZV] motor to unlock the rotary tumbler.

P80.35-2332-00

A Transmitter key
1 Locking button
2 Unlocking button
3 Open folding top button (cabrio)

Open rearend door button (coupé)

4 PANIC button

Introduction of the smart fortwo, Model Series 451

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PANIC alarm

Central locking

Body

Speeddependent locking

Pressing the PANIC button for at least 1 s triggers an
acoustic alarm. The turn signal indicators also flash.
The alarm is deactivated when

• Circuit 15 is switched ON or

• The PANIC button is pressed

Unlocking and locking from the inside via the
switches in the cockpit switch group

When the side doors and the rearend door are
closed, pressing the "Lock or unlock" switch in the
cockpit switch group causes a signal to be sent
straight to the SAM control unit. This actuates the
central locking motors. The vehicle doors and the fuel
filler flap are either locked or unlocked accordingly
and the rearend door handle switch is either enabled
or disabled.

Special function:

If the vehicle cannot be locked using the transmitter
key due to a flat battery in the key, proceed as follows:

• Open driver door

• Switch circuit 15 ON

• Actuate inside CL [ZV] switch

• Within 5 s, switch circuit 15 OFF and remove
transmitter key

• Close driver door, vehicle is locked.

Manual unlocking of the driver door with the trans
mitter key at the door lock

When the door lock on the driver door is operated with
the transmitter key, the driver door and (if the on
board power supply voltage is sufficient) the fuel
filler flap are unlocked.
If the antitheft alarm system on the vehicle is armed,
an alarm is triggered.

The vehicle is automatically locked if circuit 15 is ON
and the vehicle speed exceeds 8 mph (14 km/h).
Speeddependent locking can be activated or deacti
vated as required.

Relocking

This function relocks the vehicle automatically if none
of the doors is opened 60 s after unlocking.

Emergency opening after crash recognition

This functions unlocks the doors after an accident
that triggers a crash signal.

Remote rearend door opening (smart fortwo coupé
only)

When the "Open rearend door" button on the trans
mitter key is pressed, it sends a radio signal to the
SAM control unit. This checks the access authorization
of the transmitter key. If the access authorization is
valid, the SAM control unit actuates the trunk lid CL
[ZV] motor directly.

Remote folding top opening (smart fortwo cabrio
only)

When the "Open folding top" button on the transmitter
key is pressed, it sends a radio signal to the SAM
control unit. This checks the access authorization of
the transmitter key. If the access authorization is
valid, the SAM control unit actuates the electric soft
top motor directly.

i Note

The radio signal for unlocking the door is picked
up by an antenna integrated in the SAM control
unit. There is no external antenna for the central
locking.

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97

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Central locking

Body

1 Unlocking/locking request
2Doors status
3 Rearend door status
4 Unlocking/locking actuation
5 Rearend door unlocking request
6 Visual feedback actuation
7 Rearend door unlocking actuation
8 Unlocking via inside door opener request

9 Inside unlocking/locking request
10 Emergency opening request
11 Rearend door opening request (coupé)
12 Open soft top actuation (cabrio)
13 Open soft top request (cabrio)
14 Vehicle speed

A1 Instrument cluster
E1e5 Left turn signal light
E2e5 Right turn signal light
E3e11 Left brake/turn signal light
E4e11 Right brake/turn signal light

P80.20-3177-00

E22/1 Left additional turn signal lamp
E22/2 Right additional turn signal lamp
M12/6 Electric soft top motor (cabrio)
M14/5 Right door CL [ZV] motor
M14/5s1 Right door CL [ZV] microswitch
M14/6 Left door CL [ZV] motor
M14/6s1 Left door CL [ZV] microswitch
M14/7 Rearend door CL [ZV] motor
M14/10 Fuel filler flap CL [ZV] motor
N2/7 Restraint systems control unit
N10/10 SAM control unit
S6/1 Cockpit switch group
S6/1s1 Hazard warning flasher switch
S6/1s11 Inside unlock CL [ZV] switch
S6/1s12 Inside lock CL [ZV] switch
S15 Remote trunk opening switch

(coupé)

S17/8 Trunk lid rotary tumbler microswitch

(cabrio)

S88/9 Rearend door handle switch

A Transmitter key
CAN Controller Area Network

(data bus/CAN bus)

98

Introduction of the smart fortwo, Model Series 451

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ATA [EDW] system

Antitheft alarm system (ATA [EDW])

Body

The antitheft alarm system (ATA [EDW]) monitors all
relevant inputs for their nonactuated state. If a
change of status is detected at one of the monitored
inputs, an acoustic and visual alarm is issued.

The acoustic signals are output by the alarm signal
siren with inclination sensor. The visual signals are
output via the turn signal indicators. The SAM control
unit is the master control unit for the antitheft alarm
system (ATA [EDW]).
When armed, the antitheft alarm system (ATA [EDW])
monitors:

• The doors

• The rearend door

• The alarm siren with inclination sensor

• The position change of the vehicle

• Movements in the interior compartment

Activation and deactivation

The antitheft alarm system (ATA [EDW]) is activated
when the vehicle is locked with the transmitter key.
The antitheft alarm system (ATA [EDW]) is deacti
vated by unlocking the vehicle with the transmitter
key or by inserting an authorized transmitter key in
the ignition lock and turning circuit 15 ON.

Alarm triggering

An alarm is triggered when the SAM control unit
receives a status change from the following compo
nents:

• ATA [EDW] microwave sensor

• Inclination sensor in alarm siren

• Trunk lid rotary tumbler microswitch

• Right door rotary tumbler microswitch

• Left door rotary tumbler microswitch

Alarm output

The alarm is output via the turn signal indicators and
the alarm siren with inclination sensor.

Interior protection/towaway protection

The ATA [EDW] microwave sensor is activated approx.
30 s after the vehicle is locked. Interior protection
can be deactivated using the towaway protec
tion/interior protection switch.

The inclination sensor in the alarm siren with inclina
tion sensor registers a positional change of the
vehicle. The inclination sensor, and thus the towaway
protection, can be deactivated using the towaway
protection/interior protection switch.

The interior protection or towaway protection is
reactivated automatically the next time the vehicle is
locked.

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