SKODA Self Study Program 26 – Active and passive safety in the OCTAVIA SSP-26-Octavia-Vehicle-safety

Technical progress in vehicle engineering is constantly
perfecting vehicles in terms of active safety and is helping, more
than ever, to prevent or minimise the consequences of accidents
in the passive field.

Our safety engineers have implemented further measures in
terms of active and passive safety in the

For instance, the antilock brake system has been equipped with
additional functions, the existing safety system of airbag and seat
belt tensioner has been enlarged to include side airbags for driver
and front passenger.

The anti-theft alarm system also now features additional
components.

Š

KODA OCTAVIA.

SP 26-5

We wish to present the design of these modified systems in this
Self Study Programme and to explain how they operate

2

.

4

32

34

35

Contents

ABS 4

Antilock brake system
System overview

ABS + EBD 7

Electronic brake force distribution EBD

ABS Sensors 8
ABS Actuators 11

ABS 12

Brake function with antilock control

EDL 16

Function description

5

7

12

18
ESBS 22

EBC 24
CAN BUS 25
ABS Self Diagnosis 26
ABS Service 27
ABS/EDL Function Diagram 28
Pedal Assembly 30

ABS Knowledge 31
Side Airbags 32

Task and function
Service work
Self-diagnosis
Function diagram

36

Alarm System 38
Test Your Knowledge 44

You will find notes on inspection and
maintenance, setting and repair instructions
in the Workshop Manual.

Service

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Service

3

ABS

Antilock brake system - ABS

ABS unit Wheel sensor Brake pressure line

You will be familiar with the operation and
design of the antilock brake system MK20
from the

The tried-and-tested self-contained hydraulic

modular system of the 4-channel version has
now been enlarged in the
include electronic controls and solenoid
valves which make it possible to integrate
additional functions in respect of vehicle
dynamics.

The ABS unit

ABS/EDL-ITT Mark 20IE

differs externally by the hydraulic unit which
is 30 mm longer to accommodate the
additional valves (dimension a = 130 mm).

Š KODA FELICIA.

Š KODA OCTAVIA to

SP26-1

Sensor line

Electric motor

Hydraulic unit

a

We recognize from the designation IE that this
unit has been enlarged and that the control
unit is linked to the CAN BUS drive.

4

SP26-26

Electronic control unit

ABS system overview
(block diagram)

G45

V64

N55

G47

Abbreviated designation of
components - see function diagram

J104

Brake circuit

Brake circuit

K14/33K47

F

Outgoing information

Incoming information

G44

G46

SP26-25

The brake circuit is split, as before, into an X
arrangement, also known as a diagonal split.
Each brake circuit acts on a front wheel and on
the diagonally opposite rear wheel. A separate
brake line runs from the hydraulic unit to each
wheel (4-channel version).

The relevant ABS sensor system consists of
the four wheel speed sensors (G44 to G47)
with pulse rotors.

The new additional functions which the
system permits, are:

EBD Electronic brake pressure distribution
EDL

Electronic differential lock

EBC Engine braking control
TCS Traction control system

Faults in the ABS-specific range are indicated
by means of the ABS warning light (K47) and
by the brake fluid level warning light (K14/33).

The entire system is covered by the self­diagnosis.

(EBC and TCS are in preparation for the
OCTAVIA).

5

ABS

Installation position

The brake servo unit with tandem brake
master cylinder and the ABS unit are two
separate components.

As on all
system employs the vacuum servo assistance
principle, in other words a tried-and-tested
technical and economic solution (left-hand
drive models with 10” brake servo unit).

The ABS unit is a separate module which is
attached to the wheelhouse in the left of the
engine compartment. This installation
position is the same for left-hand and right­hand drive models (right-hand drive models
then have the separate 7”/8” brake servo unit
on the right of the engine compartment).

The tandem brake master cylinder is
connected to the ABS unit by flexible brake
lines.

Š KODA models, the brake servo

Brake servo
unit

Flexible brake lines

Tandem brake
master cylinder

ABS unit

SP26-3

The ABS unit

can only be separated once it has been
removed.
The hydraulic pump must not, however, be
separated from the hydraulic unit.

Note:
Please refer to the information on
service work, in particular bleeding
the brake system fitted with ABS/EDL
Mark 20IE.
You will find this in the Workshop
Manual OCTAVIA Running Gear.

Hydraulic pump V64

Hydraulic unit N55

SP26-31

ABS control unit J104

6

EBD - Electronic brake pressure
distribution

The electronic brake pressure distribution is a
fixed element of the ABS software in the ABS/
EDL-ITT MK 20IE unit.

The load-responsive brake pressure regulator
at the rear wheels is not fitted to models with
this equipment level.

Function

ABS + EBD

During a normal brake application below the
wheel locking limit, the brake application is
controlled by distributing the brake pressure.
The wheel deceleration at each wheel is
constantly monitored in this case.

The control unit detects the distribution of the
braking forces by comparing the wheel
deceleration of the front wheels with those of
the rear wheels.

If the braking forces at the rear wheels are too
high, the pressure is reduced by means of the
solenoid valves of the hydraulic unit.

What is achieved is an optimum distribution
of the braking forces with high cornering
forces at the rear wheels. The brake pressure

is controlled in such a way as to avoid the rear
wheels being overbraked.

Note:
For safety reasons, the functions of the
antilock brake system and the electronic
brake pressure distribution are
performed separately in the control
unit.
If the ABS function fails, the EBD
control, for example, remains
operational, and vice versa.
The failure of the EBD control is
signalled to the driver by the brake fluid
warning light, together with the ABS
warning light.

Braking force

Cornering force

EBV

ABS

Braking and cornering force

Brake slip Wheel locked

(EBV = EBD)

SP26-32

SP26-33

7

ABS Sensors

Front speed sensors G45, G47
Rear speed sensors G44, G46

Use of signal

The speed sensors supply the speed signals to
the control unit J104.

The momentary wheel speed is calculated in
the control unit.

Effects in the event of signal failure

(applies to both front and rear speed sensors)

Failure of a speed sensor:
The ABS/EDL system is switched off.
The EBD function is retained.
ABS warning light (K47) comes on.

Front speed sensor

Pulse rotor for front speed sensor

Rear speed
sensor

SP26-35

Failure of both front or rear speed sensors:
The ABS/EDL/EBD system is switched off.
Both system warning lights come on.

Self-diagnosis/Fault message

All the speed sensors are covered by the self­diagnosis.

Specific information can be retrieved in the
functions
02 - Interrogating fault memory
08 - Reading measured value block.

Pulse rotor for front speed
sensor

Electric circuit

G44 G45 G46 G47

22 23 20 19 65 21

SP26-36

J104

SP26-37

8

Pulse rotor and speed sensor

The speed sensor consists of a permanent
magnet and a coil.

This is connected to the control unit. The
speed sensor operates on the principle of a
generator, in other words when the gearwheel
of the pulse rotor rotates in front of this
sensor, a sinusoidal alternating voltage is
generated in the coil.

The frequency is depending on the wheel
speed.

The control unit converts the sinusoidal speed
sensor signals and calculates the momentary
wheel speed.

Pulse rotor at rotating
wheel

Magnetic lines
of force

Permanent magnet
in speed sensor

SP26-39

Note:
The gap between the pulse rotor

and the speed sensor is of major
significance for proper operation of
the ABS system (the signal amplitude
ù is influenced by this).

When driving, the wheel bearing play
and the movement of the suspension
result in a slight movement of the
wheel speed sensor.
The size of the gap alters.
That is why, it is important to check
the gap as specified in the Workshop
Manual when carrying out installation
work.

If an excessive gap exists, the control
unit switches off the control at this
wheel.
Dirt which can clog the teeth gap in
the pulse rotor are also sources of
faults in the ABS system.

U

Sinusoidal alternating voltage

T = Period of oscillation
t = Time
U = Voltage
ù = Signal amplitude

T

•

t

SP26-38

9

ABS Sensors

Brake light switch F

Task

The brake light switch is located at the pedal
assembly.

It operates as a normally-open (NO) contact,
its main function being to switch on the brake
lights. The function is used at the same time
for transmitting a signal to the ABS control
unit.

Use of signal

The “Brake operated” signal is required in the
ABS control unit for achieving improved
comfort during an ABS/EBD control (the brake
pedal pulsates less if the control is more
accurate).

SP26-40

In the absence of these signals, it would be
possible, for example, that the control unit
interprets a deceleration of a wheel caused by
an uneven road surface as a braking
manoeuvre.

Effects in the event of signal failure

Reduced level of comfort during ABS/EBD
control. The EDL function does not operate.

Self-diagnosis/Fault message

Operational check using function
08 - Reading measured value block

Display group number 03.

No memory is stored in the fault memory of
the self-diagnosis.

Electric circuit

+30

F

18

J104

10

SP26-41

Hydraulic pump V64
Hydraulic unit N55

Tasks

These two components form a single unit and
must not be separated.

The hydraulic unit contains the control valves
of the ABS system which are used to perform
the ABS control cycle.

The hydraulic ABS energy supply is provided
by the hydraulic pump.
This operates when a control cycle is detected,
draws in brake fluid and pumps it through the
open inlet valve to the wheel brake in order to
produce the pressure required.

ABS Actuators

Hydraulic pump V64

Hydraulic unit N55

SP26-43

Effects in the event of signal failure

V64 The ABS/EDL system is switched off.

EBD function is retained.
ABS warning light comes on,

Vehicle can continue to be braked with the
normal brake system.

N55 ABS/EDL/EBD is switched off.

ABS and brake fluid warning lights come

on.

Driver has to expect altered braking
characteristics of vehicle.

Self-diagnosis/Fault message

The hydraulic pump is covered by the self­diagnosis in function 02 - Interrogating fault
memory, and can be tested in function 03 ­Final control diagnosis.

Electric circuit

J104

V64

The hydraulic unit is tested by means of the
self-diagnosis.

M

SP26-44

11

ABS

Braking function with antilock
control

Brake master cylinder

Outlet valve

Inlet valve

Hydraulic unit

No voltage exists at valve

SP26-46

Initiating braking
operation

Brake pressure

Wheel speed

Wheel brake

Initiating braking operation - increasing brake
pressure

The brake pressure is increased by the brake
master cylinder during a brake application.

The brake pressure passes through the open
inlet valve (de-energized) to the wheel brake.

The outlet valve is closed (likewise de­energized).

Voltage exists at valve

t

SP26-50

The speed of the wheel continues to reduce
until the ABS control unit detects a tendency
for the wheel to lock from the signal supplied
by the wheel speed sensor.

To make it easier to understand, the
control operation is described only at
the control circuit of one wheel and
only those components involved are
explained.

12

Inlet valve

Outlet valve

No voltage exists at valve

Voltage exists at valve

Pressure holding phase

If a wheel is tending to lock, voltage is applied
first of all to avoid any further increase in the
brake pressure at the inlet valve.

Pressure holding
phase

SP26-47

Brake pressure

Wheel speed

t

SP26-51

The brake pressure between the inlet valve
and outlet valve remains constant during this

phase (pressure holding phase).
As a result of this, the valve is closed.
The outlet valve remains de-energized and is

thus also closed.

Note:
Note the following special design
feature for function reasons.
Inlet valve = open when de-energized;
Outlet valve = closed when de-energi­zed;
(this is important so that the brake
system can also build up pressure
without ABS).

13

ABS

Outlet valve

Brake master cylinder

Inlet valve

Pressure reduction phase

Low-pressure reservoir

Hydraulic pump

No voltage exists at valve

Voltage exists at valve

SP26-48

Brake pedal moves up

Pressure reduction phase

Brake pressure

Wheel speed

t

SP26-52

If the speed of the wheel continues to drop
although a constant brake pressure exists and
the tendency for the wheel to lock also exists,
the brake pressure must then be reduced.

Voltage is applied to the outlet valve for this
purpose.
As a result of this, the valve is opened.
The brake pressure is reduced through the
low-pressure reservoir.

The inlet valve continues to be energized and
is thus closed.

14

The hydraulic pump operates and pumps
brake fluid out of the low-pressure reservoir
into the brake master cylinder.

The brake pedal moves slightly up as a result
of this.

The wheel which is at risk of locking is again
accelerated and gains speed.

Outlet valve

Inlet valve

Low-pressure reservoir

No voltage exists at valve

Voltage exists at valve

Pressure increase phase

An increase in the pressure is necessary from
a certain wheel speed in order to achieve
optimum braking.

The inlet valve is de-energized for this
purpose.
As a result, the valve is opened.
The outlet valve is likewise de-energized and
is thus closed.

Hydraulic pump

The hydraulic pump continues operating,

draws the remaining brake fluid out of the

low-pressure reservoir and pumps it into the

brake circuit (hydraulic brake servo

assistance).

The wheel is once again braked as the brake

pressure rises.

The wheel speed is reduced.

SP26-49

Pressure increase
phase

Brake pressure

Wheel speed

t

SP26-53

These control phases of the antilock brake system are repeated as much as
5 - 6 times a second and wheel.
They are detectable from a pulsating movement at the brake pedal!

15

EDL

M

B

R

---------

What is the effect of the

Electronic
Differential
Lock

As a result of the differential, 50 % of the
available driving torque M

driven wheel provided wheel adhesion is
adequate.

If driving on a road surface which is slippery
on one side and where wheel adhesion is not
adequate, the wheel with the lower adhesion
determines the level of the driving torque
transmitted 1/2xM

Taking into account the effective radii R, the
two driving forces F are the result of the
driving torques1/2xM

.

A

is active at each

A

.

A

?

New!

50% 50%

M

A

2

M

A

M

2

FF

R

A

Important:

The wheel on the road surface providing good
grip, only transmits as much driving force as
the poorer adhesion permits (always 50 : 50).
That is why, it is possible to transmit only a
part of the total driving force available for the
vehicle. The total tractive force F

product of the subtotal of the two available
driving forces F.

If the adhesion limit is exceeded, the right­hand wheel spins (see diagram).

This is detected by the wheel speed sensor
and signalled to the ABS/EDL control unit.

The control unit thereupon activates a gentle
and controlled braking of the wheel.
This produces the braking torque M

The wheel which is not slipping, is now able to
transmit an additional tractive force F
is the result of the braking torque M
radius R of the slipping wheel.

Result:
Added traction as a result of the additional
driving force F
force F

tot 2.

Note:

F

tot 2

. The result is the tractive

EDL

> F

tot 1

1 is the

tot

.

B

and the

B

EDL

. This

Driving forces without differential lock

F

= F + F

tot 1

F

EDS

M

B

Driving forces with electronic differential
lock (EDS = EDL)

F

=

EDL

F

= F + F + F

tot 2

EDL

SP26-23

FF

R

SP26-24

16

Driving force/climbing ability of vehicles with and
without EDL on a road surface slippery on one side

N

F

tot 2

Driving force

F

tot 1

SP26-58

The electronic differential lock is an addition
to the ABS, as you will already be familiar with
from the FELICIA and OCTAVIA.

Based on the components of the ABS, the
electronic differential lock supplements the
safety offered by this system and improves
traction when road conditions are particularly
unfavourable, with a road surface which is
slippery on one side. The advantages of this
system are fully felt when starting off,
accelerating or climbing a hill.

For the EDL function, the ABS unit has been
enlarged to include additional valves and
elements of the electronic control.

Front-wheel drive with EDL
Front-wheel drive without EDL

The electronic control unit detects the speeds

of the driven wheels by means of the speed

sensors of the ABS, and constantly compares

them.

If differences in speed arise, as is the case

when a wheel begins slipping, the slipping

wheel is automatically braked by the ABS/

EDL-MK20 unit through the wheel brake to the

point at which it has approximately the same

speed as the wheel which is not slipping.

What is produced is the braking torque M

which, if need be, has the effect of a

mechanically locked differential.

The wheel with the better adhesion properties

is able to transmit a higher driving force.

SP26-22

,

B

17

EDL

Function description

To simplify understanding of the system, only
the control loop of one wheel is shown.

The braking operation is initiated by
depressing the brake pedal.

ABS/EDL hydraulic unit

Outlet valve

Suction
valves

Hydraulic pump

Brake master cylinder

Inlet valve

Wheel brake

During a brake application, the brake pressure is
increased by the brake master cylinder

The hydraulic switchover valve closes when
the pressure is increased manually.

No voltage exists at the check valve with
pressure limiter and at the inlet valve; both are
open.

Pressure valve

No voltage exists at valve

Voltage exists at valve

.

Hydraulic switchover
valve

Check valve with
pressure limiter

SP26-27

Note:
The ABS/EDL hydraulic unit is
recognizable from the longer valve
block. In addition to the ABS valves,
the ABS/EDL system features two
solenoid valves (check valves with
pressure limiter) and two hydraulic
switchover valves in the brake circuits
of the front wheel.

The brake pressure flows through both valves
to the wheel brake.

18

Pressure increase with EDL

If the ABS/EDL control unit detects a slipping
driven wheel during acceleration from the
signals transmitted by the wheel speed
sensors, the EDL function is activated.

Hydraulic pump

Wheel brake

The inlet valves of the rear wheel brake
circuits are closed. Consequently, the rear
wheels are not braked during the EDL
function.

Voltage is supplied to the check valve with
pressure limiter, and the valve closes.

The hydraulic pump is operated. It pumps
brake fluid out of the brake master cylinder to
the wheel brake of the wheel which is
slipping.

Check valve with
pressure limiter

No voltage exists at valve

Voltage exists at valve

SP26-28

The slipping wheel is braked.

The closed check valve prevents the brake

fluid in the brake circuit of the slipping wheel,

flowing back to the brake master cylinder.

The task of the pressure limiter is to limit the

brake pressure produced by the hydraulic

pump.

19

EDL

Pressure holding phase with EDL

Outlet valve

Hydraulic pump

Inlet valve

Wheel brake

If the ABS/EDL control unit detects a
decreasing acceleration tendency at a wheel
on the basis of the signals supplied by the
wheel speed sensor, the hydraulic pump is
first of all switched off in order to avoid any
further increase in pressure.

No voltage exists at valve

Voltage exists at valve

SP26-29

Voltage is supplied to the inlet valve and as a
result the valve is closed.

No voltage is supplied to the outlet valve and
the valve remains closed.

The slipping wheel continues to be braked.

20

Pressure reduction phase with EDL

Inlet valve

Brake master cylinder

Check valve

If the ABS/EDL control unit detects that none
of the driven wheels is slipping any more
during acceleration, on the basis of the signals
supplied by the wheel speed sensors, voltage
is no longer supplied to the inlet valve and as
a result the valve is opened.

No voltage exists at valve

Voltage exists at valve

SP26-30

The check valve is likewise opened.

As a result, the pressure to the brake master

cylinder is reduced.

The EDL function is completed.

21

ESBS

Electronic Stability Brake System
ESBS

The electronic stability brake system improves
directional stability and the steerability of the
braked vehicle by specific control actions at
the brakes.

It makes use of the sensors and actuators
which are familiar from the ABS system.
The ESBS is a further software development
in the ITT Mark 20 IE control unit.

Understeering

If the vehicle understeers, it is pushed by the
front wheels to the outside of the curve
(typical for front-wheel drive vehicles).

If a vehicle understeers during a brake
application, the maximum cornering force of
the front wheels is exceeded. The vehicle is
pushed by the front wheels to the outside of
the curve.

SP26-60

Full braking force
Braking force reduced as a result

of brake control action
Direction of vehicle during

understeering

The ABS control unit detects this situation on
the basis of the circumferential velocity of the
wheel. Based on this, the braking force at the
front wheels is reduced in order to in turn
increase the cornering forces. The vehicle is
stabilised and follows the desired steered
direction.

22

Note:
The driving situations of oversteering
and understeering can, in certain
circumstances, also occur the other
way around, in other words a front­wheel drive vehicle may oversteer or a
rear-wheel drive vehicle may
understeer.

Both are critical driving situations
which pose problems as a rule even
for skilled drivers. What they
represent is in fact an undesired
variation from the set course of the
vehicle.

Yaw moment - a torque with which a
vehicle rotates about its vertical axis
(skidding).

Full braking force

Braking force reduced as a
result of brake control action

Movement of vehicle during
oversteering

Oversteering

When a vehicle oversteers, the rear of the
vehicle breaks away to the outer edge of the
corner (typical for rear-wheel drive vehicles).

If a vehicle oversteers during a brake
application, the maximum cornering force of
the rear wheels is exceeded. The vehicle
breaks away at the rear wheels to the outside
of the corner.

The ABS control unit detects this situation on
the basis of the reduced rotational velocity at
the rear wheels and reduces the braking force
at the inside wheels.

SP26-61

Vertical axis of vehicle
Yaw moment
Counteracting yaw moment

(= correction moment)

The cornering forces at the inside wheels are

increased; this reduces a counteracting yaw

moment and the vehicle is thus stabilised.

Note:
It is not possible to either diagnose or
rectify a fault in the ESBS functions as
it is not possible to simulate the
vehicle dynamics with workshop
tools.

23

EBC

EBC – Engine Braking Control - an
additional function of the ABS

This additional function is made possible by
networking the electronic control units of the
ABS system and the engine.
The software of the two control units has been
enlarged accordingly.

This is envisaged in the OCTAVIA for Model
Year 99 for diesel engines and turbodiesel
engines.

Why have engine braking control?

When decelerating, the engine produces a
braking torque which acts on the driven
wheels and brakes the vehicle (= braking with
the engine).

On a smooth road surface, when the driver
eases off the accelerator or shifts down, this
braking torque may be sufficient to cause the
driven wheels to lock. The “engine brake”
reacts too sharply.

New!

Injection pump

Engine
control
unit

ABS control unit

SP26-45

Function of EDC control

The ABS sensors and electronic control detect

that there is a tendency for the driven wheels
to lock.

A message is sent over the CAN databus to
the engine control unit, to increase the engine
speed.

The engine control unit immediately
implements this message and the engine
speed is increased sufficiently to reduce the
braking torque of the engine to a very low
level so that the driven wheels no longer tend
to lock and the vehicle can be decelerated
stable.

The engine braking control operates over the
entire speed range of the engine.

Note:
As a result of the electronic
intervention of the engine control unit
(electronic throttle operation) the
engine speed can be increased
without any problem.

24

CAN BUS

Information with other systems
now over databus

You will already be familiar with the fact, for
example, that the engine control unit
communicates with other vehicle systems
such as the running gear and automatic
gearbox; in other words that a transfer of
information takes place.

This information transfer generally takes place
over separate wires.

On certain engine systems, as on the 1.8-ltr.
turbo engine, a CAN BUS is used for the
information transfer (you will already be
familiar with the CAN BUS in the OCTAVIA
from the convenience electronics system).

The ABS control unit has been adapted to
this information transfer and now has
2 connections for the CAN BUS H and
CAN BUS L.

New!

J

11

104

10

J104 = ABS/EDL control unit

SP26-21

The following electronic systems of the
vehicle are interlinked through the CAN BUS H
and CAN BUS L

– Motronic control unit
– ABS control unit
– Automatic gearbox control unit.

The link makes use of a twisted 2-wire cable.
The control unit communication is known as
the databus drive.

On models with a manual gearbox, in other
words not fitted with the automatic gearbox
control unit, the ABS and the engine control
units are linked through the CAN BUS.

Note:
You can find more detailed
information on the CAN BUS in Self
Study Programme 24.

Motronic control unit

CAN H

11

Ω

120

10

CAN L

ABS control unit

Ω

120

29

41

Databus drive

Automatic gearbox
control unit

3

25

SP23-29

25

ABS Self Diagnosis

The self-diagnosis

electronically monitors

– the signals of the sensors
– the operation of the actuators and
– conducts a self-check of the control unit

G45

J104

V64

N55

The colour-coded sensors and actuators
shown below are integrated in the monitoring
system and in the electrical test.

K14/33K47

F

G44

G47

The tests are conducted with the vehicle
system tester V.A.G 1552, the fault reader
V.A.G 1551 or with the vehicle diagnosis,
measuring and information system VAS 5051.

Address word: 03 - Brake electronics

The following functions are available
01 - Interrogating control unit version
02 - Interrogating fault memory
03 - Final control diagnosis
04 - Basic setting
05 - Erasing fault memory
06 - Ending output
07 - Coding control unit
08 - Reading measured value block

The ABS control unit J104 permanently
monitors the ABS and ABS/EDL systems and
stores any possible faults.

G46

SP26-54

The fault memory is read as part of the
maintenance service/inspection.

The hydraulic pump can be tested in function
03 - Final control diagnosis, as part of the
electrical test.

In addition, the function of the brake circuits
can be tested (assignment of brake lines to
wheel brakes, operation of valves).

Note:
Please refer to the Workshop Manual
OCTAVIA Running Gear for the exact
procedure for self-diagnosis of ABS
and for all the service operations.

26

Service work on the ABS

ABS Service

The ABS and the additional functions are
part of the active vehicle safety systems.

All the service operations require system
knowledge.

In particular, before commencing service
work, it is important to check the two
warning lamps which indicate faults

– ABS warning light
– handbrake/brake fluid level warning

light.

Use the vehicle system tester V.A.G 1552 for
conducting specific fault finding.

Certain tests - e.g. final control diagnosis ­necessitate raising the vehicle and rotating
the wheels. A second fitter is required for
these tests.

On vehicles fitted with ABS/EDL, initiate
function 04 - Basic setting for bleeding the
brake system/hydraulic unit.

1

4

2

7

5

3

C

8

6

O

9

Q

HELP

V.A.G.

1552

SP26-55

Warning functions of the warning lights

Indication Meaning

The rule which applies to both warning lights

is:

Both come on for a few seconds after the

ignition is switched on - self-check.

A road test is essential as, for example,

certain system faults are not detected until
the vehicle has been restarted and has
reached a speed of more than 20 km/h.

During the road test, carry out a controlled
brake application at least once (this can be
detected from the “pulsing” of the brake
pedal).

Certain rules of conduct have to be adhered
to before carrying out welding work on the
vehicle with electric welding equipment as
welding may affect the ABS system.

Brake fluid level too low or
handbrake applied.

Operational fault in ABS or
ABS/EDL, ABS switched
off. Brake servo assistance
retained.

ABS and EBD failed,
expect different braking
characteristics (brake
pressure at the rear
wheels is no longer
controlled).

27

N

ABS/EDL Function Diagram

The function diagram represents a
simplified current flow diagram and
shows the linkage of all the system
components of the antilock brake
system.

Components

F Brake light switch
F9 Handbrake indicator switch
F34 Brake fluid level warning contact
G44 Rear right wheel speed sensor
G45 Front right wheel speed sensor
G46 Rear left wheel speed sensor
G47 Front left wheel speed sensor
J104 ABS/EDL control unit
J218 Combination processor in dash

panel insert
K Diagnosis line
K14/33 Handbrake/brake fluid level

warning light
K47 ABS warning light
N55 ABS hydraulic unit
N99 Front right ABS inlet valve
N100 Front right ABS outlet valve
N101 Front left ABS inlet valve
N102 Front left ABS outlet valve
N125 Differential lock valve 1

N126 Differential lock valve 2
N133 Rear right ABS inlet valve
N134 Rear left ABS inlet valve
N135 Rear right ABS outlet valve
N136 Rear left ABS outlet valve
V64 ABS hydraulic pump
S Fuses

30
15

31

X

S13
10A

F

K

7

G44

22 2318

15

G45

20 19

Colour coding/Legend

=

Diagnostic connection

28

31

Input signal
Output signal

N125

N126 N133 N134

N55

Battery positive
Earth

G46

G47

S95AS162

30A

S163
30A

30
15

X
31

M

K47 K14/33

J218

55

65

21

49 14

J104

V64

M

CAN - BUS H

10119254

CAN - BUS L

3 1614

248

F34

F9

N136 N99 N100 N101 N102

31

SP26-2

in out

29

Pedal Assembly

Crash optimised pedal assembly

Task and function

The feet of the occupants are at risk if the
vehicle structure is severely deformed during
a severe frontal collision.

That is why the brake pedal swivels out of the
foot area in order to reduce the likelihood of
injuries to the feet of the occupants.

This swivelling action is initiated by a buckling
support.

The function is determined by the
deformation of the bulkhead. It is active
irrespective of the operation of the brake
pedal.

New!

Buckling support

Pushrod

Brake pedal

Effect of crash

– In a frontal crash, the pedal assembly is

displaced toward the central tube.

– This results in the buckling support being

deflected followed by the pushrod
buckling.

– The pedal plate is swivelled out of the way

by the excursion “s” (as much as 170 mm).

– The angular motion of the braking foot is

minimised by the buckling of the pushrod
and by the deformation work which is
produced as a result.

– The acceleration forces which normally

occur (braking foot) are considerably
reduced.

s

30

SP26-59

KNOWLEDGE

on abbreviations relating to vehicle dynamics

The abbreviations relating to the vehicle
dynamic systems differ from manufacturer
and model.
The different abbreviations often in reality
conceal identical functions.
The overview below of current abbreviations
is designed to provide you with an aid.

ABS KNOWLEDGE

SP26-20

System

ABS Antilock Brake System Prevents the wheels from locking during

ASR
ASC
ASC+T
TCP
TCS

DSA Dynamic SAfety Stabilises the vehicle during brake

Acceleration Slip Regulation
Automatic Stability Control
Automatic Stability Control+Traction
Traction Control Plus
Traction Control System

EDS
ETS

Electronic Differential Lock
Electronic Traction System

Function

brake application. Permits high braking
forces while maintaining directional stability
and steerability.

Prevents the driven wheels from slipping by
controlling the brakes and the engine
management system.
Prevents the vehicle from understeering or
oversteering when cornering.

applications and prevents the vehicle
breaking away by altering the wheel tow of
the wheel with the best adhesion.

Permits optimal starting-off on different
road surface conditions by braking the
slipping wheel.

ALD Automatic Locking Differential Permits optimal starting-off on different

road surface conditions by means of a multi­plate lock in the differential.

EBD Electronic Brake pressure Distribution Adapts the braking action of the front and

rear wheels to the particular driving
situation.

ESBS Electronic Stability Brake System Minimises understeering or oversteering if

the vehicle is braked when cornering,
improves directional stability and
steerability.

31

Side Airbags

Task and function

In a side impact, only a limited distance is
available for the deformation at the vehicle ­namely the constructional depth of the door.

Accident statistics reveal that more than 25 %
of all accidents affect the side of the vehicle.
The consequences of such accidents are
considerable because the crumple zone and
the seat belts primarily offer protection in
frontal and offset collisions.

New!

Sensors for side
airbag

The measures for side impact protection
which are offered as standard on the ŠKODA
OCTAVIA include

– door stiffeners,
– tubular stiffener in the lower door sill,
– foam-lined side impact cushion in the

doors for hip and rib area

and are now optionally supplemented by
means of side airbags for driver and front
passenger.

The side airbags considerably reduce the
injuries to the upper body in an accident.

The side airbags are located in the side
bolsters of the stable front seats which face to
the outside. The side airbag has a volume of
12 litres.

30° 30°

0°

side offset 17.2 %

side 7.2 %

Accident frequency Protected area

Side airbag

rear offset 3.6 %

SP26-7

In the event of a side impact within the
protected area shown in the illustration, the
side airbag on the side of the vehicle on which
the impact occurs, is activated.

The sensors for the side airbag are attached to
the cross members of the front seats.

The side airbags are deployed by the same
control unit which activates the front airbags.

32

SP26-4

Control unit Sensor Seat cross

member

The deployment of the side airbag plotted over
time - six phases are characteristic.

ms

1

3

501525

2

4

5

40 60

6

SP26-8

The technical problem which is encountered

in developing the side airbags is the fact that
they must inflate even more rapidly than the
front airbags, and the sensor has to be able to
reliably detect a side impact.

As a result of the electronic analysis, it is
possible for the side airbags to provide their
protective function in an accident within only
15 ms.

Note:
The sensor reacts only to an impact
from the side or offset at the side,
where the protective function requires
to be provided.
Frontal, offset and rear collisions are
not registered.

0 ms Collision - the vehicle suffers a side

impact

5 ms The electronic sensor signals the side

impact to the control unit and the
appropriate side airbag is ignited

15 ms The side airbag is inflated and has

assumed its protective position

25 ms The occupant is cushioned by the side

airbag
40 ms The side airbag deflates
60 ms The occupant moves back away from

the side wall of the vehicle

33

Side Airbag

Service work

The safety precautions which apply to the side
airbags are the same as for the driver and
passenger airbags.

When carrying out repair work, only genuine
seat covers for the backrest may be fitted.
These are recognizable from the sewn-on
inscription “AIRBAG”.

It is not permitted to use protective covers for
the backrest.

Backrest upholstery

Backrest
frame

The plug connections are protected against
inadvertent triggering by flexible short-circuit
bridges.
If an electrical connection is activated, the

plug contact positioned in the direction of the
airbag is short-circuited by means of a
resilient metal loop.

The propellant charge and the airbag system
control unit have an operating life of 15 years.

Airbag unit

SP26-9

Plug contact

SP26-10

Limited service life!

The sensor for the lateral acceleration is
identical for the left and right sides.
When installing, note: The arrow faces out
toward the door!

34

SP26-57

Self-diagnosis

As a basic rule, it is only permitted to use the
vehicle system tester V.A.G 1552, the fault
reader V.A.G 1551 or the vehicle diagnosis,
measuring and information system VAS 5051
for conducting tests.

Warning!
Carry out only a visual inspection of
the wiring!
Do not conduct any electrical
continuity test or measurement
in the ignition circuits!
Do not inspect wiring unless the
ignition is switched off!

The airbag control unit J234 which controls
the front airbags and the side airbags is
equipped with a fault memory.

It detects faults and malfunctions in the airbag
system.

1

2

3

4

5

6

7

8

9

C

O

HELP

Q

V.A.G.

1552

202_CZ_002

SP17-29

The following functions are available for the
complete airbag system:

01 - Interrogating control unit version
02 - Interrogating fault memory
03 - Final control diagnosis
05 - Erasing fault memory

06 - Ending output
07 - Coding control unit
08 - Reading measured value block
10 - Adaptation

The airbag warning light K75 is integrated in
the operational test.

This light comes on for about 4 seconds after
the ignition is switched on, and then goes out.
If it does not go out, there is a fault in the
supply voltage for the control unit. Interrogate
the fault memory in this case.
If the warning light comes on again, this also
indicates a fault. Interrogate the fault memory.
If the warning light constantly flashes, it is
then necessary to replace the control unit.

Airbag warning
light

4

3

1/min x 1000

5

2

1

6

7

120

100

140

km/h

80

160

60

40

180

20

200

220

240

SP26-11

Note:
Please refer to the Workshop Manual
OCTAVIA Body Removal and Fitting
Work for the exact procedure for self­diagnosis.
You will also find information
regarding deactivating the passenger
airbag in this document.

35

Side Airbag

Function diagram

The function diagram presents a simplified current
flow diagram. It shows the linkage of all the system
components of the airbag system with driver airbag,
passenger airbag, side airbag for driver side and
passenger side.

Components

D Ignition/starter switch
F138 Airbag coil connector/return spring with

slip ring
G179 Side airbag crash sensor, driver’s side
G180 Side airbag crash sensor, front passenger’s

side
J218 Combination processor in dash panel insert
J234 Airbag control unit (with deployment

sensors)
J393 Convenience system central control unit
K75 Airbag warning light (in dash panel insert)
N95 Airbag igniter - driver’s side
N131 Airbag igniter - front passenger’s side
N199 Side airbag igniter - driver’s side
N200 Side airbag igniter - front passenger’s side

Legend

Diagnostic connection

Earth bridges

Colour coding

Input signal

Output signal

Positive

Earth

Earth connection

M = Earth connection of airbag control

unit by means of 3 bolts on floor
tunnel

Positive connection

A2 = Positive connection -15- in wiring

loom

36

30
15

X

31

30
15

X

31

10 11

F138

30

14 13

J218

9

J 234

K75

20 21

30

D

15

A2

5 34

34 21

J393

31

+

N95

-

-

N131

M

+

G179

in out

-

G180 N199 N200

+

-

+

SP26-6

37

Alarm System

Anti-theft alarm system with
interior monitor

D

C

E

F

New!

D

G

D

H

D

The anti-theft alarm system with interior
monitor is part of a further generation of the
vehicle convenience system.

The anti-theft alarm system monitors the

following parts of the vehicle:

– all the doors
– tailgate
– bonnet
– ignition lock
– interior of vehicle

The warning system is automatically switched
on when the driver’s door or the tailgate is
locked.

This is done by means of the car key or by the
radio remote control if a locking operation is
performed.
If you wish to lock the vehicle without
switching on the warning system, the locking
operation must then be performed twice
within 5 seconds.

B

A

System components

The existing components of the convenience
system and the additional components are
interlinked for the anti-theft alarm. The
additional components are shown encircled.

A Convenience system central control unit

J393
B Anti-theft alarm signal horn H 8
C Bonnet contact switch F120 in lock of

bonnet
D Rotary tumbler switch in door locks
E Interior motion sensor G273
F Ignition lock
G Contact switch in lock cylinder of tailgate
H Central locking warning light K133

SP26-15

38

Indication of anti-theft alarm operational

When the anti-theft alarm system is switched
on, all the turn signal lights flash once to
indicate that the system is operational.

An indicator light is positioned next to the
interior locking button of the driver’s door.

It flashes when the warning system is active.

Note:
If the warning system remains
activated over a lengthy period, the
warning light goes out after 28 days.
This ensures that no current is drawn
from the car battery if the car is parked
for a lengthy period. The system itself
remains operational.

Interior locking button

SP26-14

Indicator light for central locking
and anti-theft alarm system

The alarm signal

The sensors of the anti-theft alarm system
signal an unauthorized attempt to enter the

car to the central control unit if

– a door is opened
– the tailgate is opened
– the bonnet is opened
– the ignition is switched on
– the side windows of the car are smashed

in.

The control unit activates all the turn signal
lights of the vehicle and the alarm horn.

The visual and audible alarm sounds for
approx. 30 seconds.

If a further attempt is made to break into the
car after this period, the alarm is once again
triggered.

SP26-16

39

Alarm System

Interior monitor

Operating principle

The interior motion sensor G273, a microwave
sensor, monitors the interior of the vehicle. It
creates a cubic monitored area in the interior
of the car.

The sensor detects any changes within this
monitored area.

The motion alarm system reacts if there is a
breach of the integrity of the space, for
example an attempt to break into the car if the
windows of the car are smashed in.

Design

Console for glove
box

Components of the motion alarm system

– convenience system control unit J393
– interior motion sensor G273

The sensor is attached in the middle of the car
by an angle bracket to the console of the glove
compartment. It is located behind the ashtray.

The motion alarm signal is an addition to the
anti-theft alarm system and is activated
together with the latter.

The anti-theft alarm system and motion alarm
system interact.

Switching off the interior motion sensor

It is possible to switch off the interior motion
sensor manually when the anti-theft alarm is
activated.
To do this, press the remote control “closed”
twice.
The anti-theft alarm then operates without the
interior motion sensor.
This programme must be coded separately in
the convenience system central control unit,
this being done with address word 46,
function 10 - Adaptation, channel 05.
The procedure is described in the Workshop
Manual.

Angled bracket

SP26-62

Interior motion sensor
G273 (microwave sensor)

Note:
A certain period of time elapses from
switching on the monitoring system
until it is operationally ready.
During this time, the microwave sensor
creates its cubic monitored area and
carries out a self-check.
The time period is displayed visually by
the flashing frequency of the indicator
light.
The light begins with a higher
frequency and after about 30 seconds
continues flashing with a lower
frequency.
The system is then activated.

40

Block diagram of anti-theft alarm system with
interior motion sensor G273

Interior motion sensor G273
(microwave sensor)

Radio remote control

Aerial for central locking and
anti-theft alarm system

M5

M18

30

J386

J393

K133

J388 J389

CAN H

CAN L

F120H8

J387

M19

M7

M6

Sensors

– Aerial of radio remote control
– Interior motion sensor G273
– Control units J386, J387, J388, J389 in the

doors
– Bonnet contact switch F120
– Tailgate central locking switch F218

F218

M8

Actuators

– Anti-theft alarm signal horn H8
– Turn signal lights M5, M6, M7, M8, M18,

M19
– Central locking warning light K133

Note:
The information from the door control units
passes over the CAN BUS.
The interior motion sensor, alarm horn and
bonnet contact switch are connected to the
convenience system central control unit over
direct cables.

SP26-63

41

Alarm System

Self-diagnosis

The anti-theft alarm system with the interior
motion sensor features a comprehensive self­diagnosis.
If faults occur at the system components, fault
codes are stored in the fault memory of the
control unit.
Self-diagnosis can be performed with the
vehicle system tester V.A.G 1552, the fault
reader V.A.G 1551 or with the vehicle
diagnosis, measuring and information system
VAS 5051.

Address word: 46 - ignition switched on

(as for convenience system, the control unit
version is enlarged by the function of the anti­theft alarm system)

1

2

3

4

5

6

7

8

9

C

O

HELP

Q

V.A.G.

1552

202_CZ_002

SP17-29

Once the link to the system has been
established, it is possible to select the
individual functions also with the ignition
switched off.

The following functions are available:

01 - Interrogating control unit version
02 - Interrogating fault memory
03 - Final control diagnosis

05 - Erasing fault memory
06 - Ending output
07 - Coding control unit
08 - Reading measured value block
10 - Adaptation

You can find, for example, a list of the alarm
sources in function 08 - Reading measured
value block, display group 15.

Please refer to the current Workshop Manual
OCTAVIA Body Removal and Fitting Work for
the individual fault codes.

Note:
A practical operational check of the
interior motion sensor can be carried
out as follows:
– Open a side window about 10 cm.
– Lock vehicle and arm system.
– Wait until indicator light flashes

slowly.

– Place your hand through the

opening of the window into the
monitored area of the microwave

sensor.
If the system is operating properly, the
alarm will be triggered.

42

Function diagram of alarm system

The function diagram represents a simplified
current flow diagram. It shows the linkage of
the anti-theft alarm system to the components
of the interior monitoring system and the
convenience system.

30

15

S38

S14412S111

15

8 9 11 1

R47

10 7

K133 J386 J387 J388 J389

J393

2 4 23 13

14

M7

M5

CAN - BUS H

30

15

CAN - BUS L

96

G273

31

Legend

Positive
Earth
Input signal
Output signal

H8 F120 F218

F120 Bonnet contact switch
F218 Tailgate central locking switch
G273 Interior motion sensor
H8 Anti-theft alarm signal horn
J393 Convenience system central control

K133 Central locking warning light
S Fuse
R47 Aerial for central locking and anti-

Refer to the block diagram on page 41 for the
designation of the other components.

M8

M19

unit

theft alarm system

M6

M18

31

SP26-64

43

?

Test Your Knowledge

Which answers are correct?
Sometimes only one.
But perhaps also more than one - or all of them!

1. The new antilock brake system offers a range of
additional functions. The relevant ABS unit is:

A. on the outside not distinguishable from the

conventional ABS unit
B. recognizable from the longer hydraulic unit
C. equipped with an enlarged software for the

additional functions

2. What are the advantages which the electronic differential lock offers?
A. improvement in traction on unfavourable road surfaces when braking.

B. improvement in traction on unfavourable road surfaces when

starting off and accelerating.

C. offers, if need be, the effect of a mechanically locked differential.

3. For operational reasons, the electromagnetic inlet and outlet valves
for the wheel brake are:

A. always open when de-energized
B. always closed when de-energized
C. inlet valve open when de-energized and outlet valve closed

when de-energized

?

4. The electronic differential lock uses existing components of the ABS.
These are supplemented by:

A. two solenoid valves in the hydraulic unit
B. additional wheel speed sensors at the driven axle
C. an enlarged software in the control unit

5. Each wheel is fitted with a wheel speed sensor and a pulse rotor;
there is a gap between both of these components.

A. The gap between the pulse rotor and wheel speed sensor

is of no significance for operation.
B. The gap influences the signal amplitude and therefore must be checked.
C. If the gap is excessive, the ABS control unit activates

an emergency running mode.

44

?

6. The engine braking control is possible:
A. by using the ABS sensors as additional information for the engine control unit

B. by enlarging the software of the control units
C. by interlinking the ABS and engine control units

7. Driver and front passenger seats are equipped with an airbag for side impacts.
Is it necessary to replace the units after a certain vehicle operating period?

A. These units require no maintenance and do not need to be replaced.
B. After a vehicle operating period of 10 years.
C. After a vehicle operating period of 15 years.

8. Which precautionary measures require to be taken when removing a front
seat fitted with a side airbag?

A. The earth circuit of the airbag system should be closed by using an adapter.
B. The fitter has to electrostatically discharge himself before

separating the plug connections to avoid the airbag being activated.

C. The airbag control unit must be removed first of all to avoid the

airbag being activated.

9. The interior monitoring system is:

A. an additional function of the anti-theft alarm system
B. an optional equipment which replaces the anti-theft alarm system
C. active each time the vehicle is locked conventionally. For this reason,

small animals must not be left in the vehicle otherwise the system
would be activated.

10. The anti-theft alarm system
A. has its own system of sensors, actuators and control.

B. uses the sensors and the control unit of the central locking system.
C. uses the sensors and the control unit of the convenience system

and is enlarged by additional sensors and actuators.

1. B., C.; 2. B., C.; 3. C.; 4. A., C.; 5. B.; 6. A., B., C.; 7. C.; 8. B.; 9. A., C.; 10. C.
Answers

45

Notes

46