TRAINING TIPS

AND TACTICS

Truck Air and Brakes

- Management

General information

EBS general description

Modulators
Footbrake valve
Back-up mode
Port numbers
Basic fault nding logic
Use IMPACT

EBS Generation 2

Main components
Axle conguration
Circuit diagram - general
Circuit diagram - air pipes
Circuit diagram - wires/
datalinks
EBS ECU location and plugs
Wheel speed sensor (WSS)
Lining wear sensor (LWS)
Footbrake valve

Contents
11
13
15
15
17
21
23

27
29
32
35
37
39
41
45
47

EBS Generation 2 - cont.

Modulator - single channel

Modulator - twin channel
Modulator - trailer
Automatic brake adaptation Brake Compatibility System
(BCS)
Load sensing
Traction Control System (TCS)
Trailer Brake System (TBS)
Differential lock
Test equipment
Footbrake valve test
Modulator test
EBS ECU test
VCADSPro - EBS
Truck/trailer ABS lights and symbols
ABS test

49
57
59
60
63
65
67
69
71
71
71
73
75
77
77

EBS Generation 3

Axle conguration
Main differences
Software levels
Electronic Stability Program
(ESP)
Hill start aid
Automatic differential lock
Status recorder
Emergency Brake Assist (EBA)
Drag torque control
Wake-up signal
Brake temperature warning
Brake Blending Function (BBF)
Wheel brake monitoring
Load sensing
External Brake Demand (EBA)

80
83
86
86
89
91
93
93
93
95
96
96
97
97
98

EBS Generation 3 - cont.

Brake force distribution/

slip control
EBS ECU location and plugs
Modulators
ABS control valve
Multi-channel systems
Three channel 4 x 2
Three channel 6 x 4
Four channel 6 x 2 pusher
Four channel 8 x 4
Five channel 8 x 2
Footbrake valve test
Modulator test
Trailer modulator test
EBS ECU test
Resetting learning parameters

99
101
103
105
110
113
115
117
119
121
123
125
127
129
131

Introduction
About this
Pocket guide

This guide is intended as a memory jogger for the

knowledge you have gained during your training course.
The guide includes a summary of the material covered in:

Truck Air and Brakes - Management

Danger,
Warning,
Caution &
Note

In this guide, risk of injury or damage is indicated by the

following headings:
DANGER - indicates a risk of serious personal injury or
death.
WARNING - indicates a risk of personal injury, or severe
product damage.
CAUTION - indicates risk of product damage.
Note - draws attention to special methods or particular
features.
Read and implement all DANGER, WARNING and
CAUTION instructions.

Replacement
parts

When replacement parts are required, it is essential that

only Volvo genuine parts are tted. If Volvo genuine parts
are not used:
- safety features embodied in the vehicle or components
may be impaired.
- performance and/or operation of the vehicle or
components may be adversely affected.
- Volvo warranty terms may be invalidated.

Specication

Volvo are constantly seeking ways to improve their

products, and alterations take place accordingly.
Whilst every effort has been made to ensure the accuracy
of this guide, it should not be regarded as an infallible guide
to current specications of any product.
Neither Volvo, nor the supplier of this guide shall, in
any circumstances, be held liable for inaccuracy or the
consequences thereof.

Copyright

All rights reserved. No part of this publication may be

reproduced, stored in a retrieval system, transmitted or
copied without written permission from Volvo Truck & Bus
Ltd.
Volvo Truck & Bus Ltd. 2005

General information
9

General information
33

ECU

37

11
12

37
S

33
Air supply - constant
12 bar
Modulated air
pressure
Electronic control
signal

33

37a
33

10
10. Footbrake valve
11. Front circuit air tank
12. Rear circuit air tank
33. Brake chambers
37. Front brake
modulators

37a. Rear brake

modulator
ECU. Electronic
Control Unit

10

General information
EBS/ECBS
- general
description

Changing the title Electronic Brake System (EBS) to

Electronically Controlled Brake System (ECBS) provides a
more accurate start point for a description of the system.
The brake system remains mainly an air system - the
pads are still applied by air pressure via conventional brake
chambers.
The crucial difference is that, with an EBS system, air
pressure, and supply and release to and from the brake
chambers, is electronically controlled.
Electronic control is largely responsible for providing one of the
main advantages of EBS - faster application and release, with
a consequent reduction in stopping distance.
Faster response is also aided by the fact that the electronically
controlled modulator valves, which control pressure and
supply, are located very close to the brake chambers, and
have a constant air supply direct from the air tanks.
The concept is shown in the simplied diagram
above.

11

General information

2
12

General information
Modulators 1 - single channel
2 - twin channel

ABS/TCS and
load sensing

The modulators are basically solenoid controlled relay

valves, which can modulate - vary - the air pressure
supplied to the brake chamber connected to them.
They are normally controlled by electronic signals from the
EBS ECU. The pressure is modulated according to the
value of the applied electronic signal.
The value of the signal is calculated by the EBS ECU
in response to signals it receives from other sensors importantly, individual wheel speed and vehicle load.
The modulator is, therefore, providing ABS/TCS and load
sensing control, without the need for the separate valves
used in non-EBS systems.
If there is an electrical fault, the modulators are controlled
by air pressure from the footbrake valve.

13

General information
33

ECU

37

33
11

37a

12

37
S

33

10

51

Air supply - constant 12 bar

Air supply - reduced pressure
Modulated air pressure
Electronic control signal

51

10

33

10. Footbrake valve

11. Front circuit air tank
12. Rear circuit air tank
33. Brake chambers
37. Front brake modulators

37a. Rear brake modulator

51. Pressure limiting valves
ECU. Electronic Control Unit

14

General information

Footbrake valve

Back-up mode

The footbrake valve is a conventional two part air valve,

with the addition of two potentiometers.
The potentiometers supply electrical signals to the EBS
ECU, which are proportional to footbrake movement - i.e.
driver demand.
When EBS is operating without fault, the electrical signal
reaches the modulator instantaneously, and is the only
driver demand signal used by the modulator.
Air pressure is still delivered from the footbrake valve, but
electrical control takes priority.
However, if an EBS fault occurs, the system goes into
back-up mode, in which the driver demand signal reverts
to air pressure from the footbrake valve - as in non-EBS
systems.
The footbrake valve is supplied with air at reduced pressure
via pressure limiting valves (51).

15

General information
Back-up mode

Note: when the system is operating in back-up mode, the

following functions are not available:
Anti-Lock Braking (ABS)
Traction Control (TCS)
Tractor/trailer brake adaptation (BCS)
Load sensing
Because ABS and load sensing are not available, braking
is biased towards the front axle and trailer brakes.
When the footbrake pedal is pressed air, at up to 2 bar
pressure, is delivered to the front brake circuit and trailer
circuit, before air is delivered to the drive axle circuit.
This bias reduces the risk of a jack-knife occurring.

16

General information
Port numbers
- general

Valve ports generally conform to a common numbering

sequence:
Port 1 - Supply, normally from a tank. If there is more than
one supply, a second number is used - e.g. 11, 12.
Port 2 - Delivery, to another component. If there is more
than one delivery, a second number is used - e.g. 21, 22.
Port 3 - Exhaust, to atmosphere.
Port 4 - Signal to the valve to operate.
Port 0 - To atmosphere - on the compressor from the air
inlet.
Port 5 - To the re-generation tank.

17

General information
11

11

Note: Other ports 11 and 12 to

pressure gauges.
For EBS, the front circuit is the
primary circuit.

21
22

11 - from front tank (11)

12 - from rear tank (12)
21 - to front modulators
22 - to rear modulator
S - Secondary system
P - Primary system

12

21 P

11

22
12

Footbrake valve ports

18

General information

Advantages of
EBS

In common with other vehicle systems - e.g. engine

management - once electronics is introduced, it becomes
possible, or easier, to take account of additional factors
which affect the nal desired result.
In summary, EBS allows easy interaction with:
- EMS, power reduction in safety critical circumstances.
- engine brake or retarder, retardation assistance.
- transmission control system.
- pad/lining wear sensing, distributed brake force for more
even wear.
Simplied use of:
- vehicle load signal, no separate load sensing valve.
- individual wheel speed signals, no separate ABS/TCS
valves (except certain Gen. 3 congurations).

19

General information
Air is leaking from a valve.

Disconnect pipe(s) from

outlet port(s) 2

Note: The valve

may need to be
operational. Operate
park/footbrake

Is air leaking from the pipe ?

Yes

No

The component connected

to the pipe is leaking. Trace
the pipe back

Renew the valve

20

General information
Basic air brake
fault nding
logic

Air pressure
units

The chart above shows the basic logic to be applied when

air is leaking from a valve.

Air pressure can be expressed in bar or Pascal:

1 bar = 100 Kpa (KiloPascal)
10 bar = 1 mPa (MegaPascal)

21

General information

Use IMPACT

To ensure that you are using the latest service

information - especially specications - always
get your information via IMPACT:
Group 56 and 59 (content varies according to
Information Type selected)

22

General information
IMPACT
Information
groups

Group 56 = modulators, footbrake valve

Group 59 = ECU

Check list A - ECU

EBS signal descriptions
Check list B - modulators
EBS signal descriptions
Check list C - footbrake valve
Comments to check list C
Brake pressure EBS

59
59
56
56
56
56
56

23

24

Electronic Braking System - Generation 2

25

9
6

2
6

6
7

8a

1 9 10
11

10
7

8b

2 4

12

8a

7 11
6
8b

12

26

EBS - Gen. 2
EBS Gen. 2 components

1. EBS Electronic Control Unit (ECU) (9082)

2. Single channel modulator* (6076)
3. Twin channel modulator (6076)
4. Trailer modulator (6076)
5. Footbrake valve (6077)
6. Wheel speed sensor (7057)
7. Brake lining wear sensor (7085)
8a. Load sensor (7064) - Signal to EBS ECU via ECS ECU
data link.
8b. Load sensor (7072) - with leaf springs.
9. Trailer brake switch (1157)
10. Traction Control (TCS) switch (1155)
11. Low pressure switch - park tank (2075)
12. Plug socket for ABS/EBS (79) ISO socket dedicated to
EBS - 7 pins
* Note: On version 2 trucks with lift axle, an extra single
channel modulator is used to control both N/S & O/S brakes
on the lift axle.
27

EBS - Gen. 2

6x2
Tag

6x2
Pusher

6x4
28

EBS - Gen. 2
Axle
conguration
Gen. 2

Service information in IMPACT refers to the axles, and to

components attached to the axles:
1 - is always the front axle
2 - is always the drive axle
3 - is either a tag or pusher axle

29

EBS - Gen. 2
11

High pressure 12 bar

Reduced pressure

P21

12

14
51

HPF

51

P11
P23

52a
57
56

P1

24

P22
P12
P24

HPR

S
P

10

30

HPF
P21

33

P1

P22

24

P11

P12

13
S
P

10

25a
25

33

SU
EM
CO
SE

P24

P23

37
37

37b

30

HPR

31

37a
33

33

EBS Gen. 2 circuit - 4 x 2

31

EBS - Gen. 2
Main components
- EBS 4 x 2

The main components of the EBS circuit

are:
10. Footbrake valve
11. Front circuit air tank
12. Rear circuit air tank
13. Park brake tank
14. Wet tank
24. MCPV (7 port)
25. Distributor manifold
25a. Filter
33. Brake chamber
37. Single channel modulator
37a. Twin channel modulator
37b. Trailer modulator
38. Pressure sensor
51. Pressure limiting valve
52a. Overow valve (6.7 - 7.0 bar)
56. Air bellows
57. Air suspension valve

HPF - high pressure

from tank (11) direct to
front modulator valves
HPR - high pressure
from tank (12) direct to
rear modulator valve
SU - supply, trailer
EM - emergency, trailer
CO - control, trailer
SE - service, trailer

32

EBS - Gen. 2
EBS Gen. 2 was the rst version to be released to the UK
market in year 2000.

33

EBS - Gen. 2

37

33

33

10
12

13
24
37

51
33

14

11

37a

37b

51

33
T
34

EBS - Gen. 2
Gen. 2 - air pipes

1. Compressor
10. Footbrake valve
11. Front circuit air tank - 12 bar
12. Rear circuit air tank - 12 bar
13. Park brake tank - 8.5 bar
14. Wet tank - 12 bar
24. MCPV (7 port)
33. Brake chamber
37. Single channel modulator
37a. Twin channel modulator
37b. Trailer modulator
51. Pressure limiting valve - 8.5 bar
T. To trailer

35

EBS - Gen. 2
33

WS

J1939 - J1587
ISO 11992

SS

37
CAN

33

WS

SS

CAN
ECU

10
CAN

37
WS

33

SS

CAN

37a
37b

38

33

WS

SS

56
36

EBS - Gen. 2

Gen. 2 - wires/
data links

10. Footbrake valve

33. Brake chamber
37. Single channel modulator
37a. Twin channel modulator
37b. Trailer modulator
38. Pressure sensor
56. Air bag
CAN. Controller Area Network
ECU. EBS Electronic Control Unit
WS. Lining wear sensor
SS. Wheel speed sensor
J1939. Fast data link
J1587. Slow data link
ISO 11992 - data link, trailer with EBS

37

EBS - Gen. 2

Elec. 98 trucks
Version 2 trucks
38

EBS - Gen. 2
EBS ECU
location

Plug colours and

markings

The illustrations above show the location of the ECU on

Elec. 98 and Version 2 trucks.
Version

Elec. 98

Version 2

EBS Gen.

Black

X1

EBA

Yellow

X2

EBB

Green

X3

EBC

Purple

X4

EBD

39

EBS - Gen. 2
1

40

EBS - Gen. 2

Wheel Speed
Sensor (WSS)

Attached to each wheel hub is a toothed pole wheel (1).

Located very close to the wheel is a sensor (2).
The sensor is an inductive signal generator, which has a
permanent magnet surrounded by a coil.
As each wheel tooth passes the sensor tip, an AC voltage
pulse is induced in the sensor coil. As the wheel rotates
faster, more pulses are generated.
The number of pulses in one second is the signal
frequency.
The frequency, and voltage, of the signal are directly
related to the speed of the wheel.
The voltage is also directly related to the air-gap between
the wheel teeth and sensor tip: wider gap = lower voltage.
A correct gap is particularly important for reliable low speed
operation.

41

EBS - Gen. 2

Frequency

Voltage

Low speed
High speed
Typical form of alternating voltage generated by an inductive sensor
42

EBS - Gen. 2
Wheel Speed
Sensor (WSS)

The induced signal is fed to the ECU of the adjacent

modulator and, from there, to the EBS ECU.
Using the speed signal, the EBS ECU can calculate:
- speed of each wheel
- road speed
- acceleration
- deceleration
Calculations are based on the formula:
Force = Mass x Acceleration
Rearranged: Acceleration = Force/Mass
The speed signal is one of the factors used by the EBS
ECU to calculate the brake force to be applied.
It is also used during ABS/TCS control, and by
other ECUs, via the J1939 data link.

43

EBS - Gen. 2

4.1 V

0.5 V
20 mm

0 mm
44

EBS - Gen. 2
Lining Wear
Sensor (LWS)

Even lining wear

Each brake calliper has an electronic wear sensor which

detects the average thickness of both brake pads.
The sensor produces a voltage varying between 0.5 V and
4.1 V depending on how much pad thickness remains.
Each time the footbrake is pressed a reading is taken.
When less than 20% of the pad lining remains, the
YELLOW information lamp is lit, and the message check
brakes is displayed.
Using information from the sensors, brake pressure is
adjusted between the front and rear axles, so that lining
wear is as even as possible. Pressure adjustment does not
alter the total braking force.
Stored values for each wheel can be read using VCADS.
Note: Using VCADS, the sensors must be
recalibrated when new pads are tted.

45

EBS - Gen. 2
4
3
1
2

11
12

21
22

5V
SM2
AGNI
SM1
4.5V

SM2

0.5V
Off

SM1
Full

46

EBS - Gen. 2
Footbrake valve

The EBS footbrake valve is a conventional two part air

valve, with the addition of two potentiometers.
The pot. output voltage varies in proportion to the amount
of pedal depression.
The voltage from each pot. is fed to the EBS ECU, and is
one of the factors used by the ECU to calculate the brake
force to be applied.
Any detected inconsistency in either voltage will cause a
fault to be recorded, and the system will revert to back-up
mode.
5V. Controlled voltage supply to potentiometers
SM2. Pot. output signal - 4.5v - 0.5V
AGNI. Common earth
SM1. Pot. output signal - 0.5V - 4.5V
11. Front circuit inlet - 8.5 bar
12. Rear circuit inlet - 8.5 bar
21. To front circuit
22. To rear circuit
47

EBS - Gen. 2

PS
WSS

LWS

CAN

WSS

ECU
IV

OV

BV

PS

4
11

37
F

RLV
3

33

48

EBS - Gen. 2

Single channel
(wheel)
modulator

1. High pressure direct supply

2. Modulated delivery
3. Exhaust
4. Back-up supply
BV. Back-up valve
IV. Inlet valve
OV. Outlet valve
PS. Brake line pressure sensor
RLV. Relay valve

F. Filter
BU. Back-up air supply
WSS. Speed sensor signal
LWS. Wear sensor signal
CAN. CAN + voltage supply
11. Air tank
33. Brake chamber
37. Modulator

Each modulator has several internal valves and an ECU.

Via a data link, the modulator ECU receives signals from
the EBS ECU, which determine the brake pressure to be
applied to the connected brake chamber.
The modulator ECU also receives signals from sensors wheel speed, lining wear, vehicle load, and transmits these
signals to the EBS ECU, where they are used to calculate
the pressure signal sent back to the modulator ECU.

49

EBS - Gen. 2

PS
WSS

LWS

CAN

WSS

ECU
IV

OV

BV

PS

4
11

37
F

RLV
3

33

50

EBS - Gen. 2

Single channel
(wheel)
modulator

In the illustration above, the ignition is on so the modulator

has power. The footbrake pedal is not pressed.
The pressure sensor monitors the pressure in the brake
chamber supply line.
The modulator ECU is receiving wheel speed and lining
wear information from the sensors.
IV is not energised and is closed.
BV is not energised and is open.
OV is not energised and is closed.
RLV is fed with air from tank (11), but has no pressure
signal.

51

EBS - Gen. 2

PS
WSS

LWS

CAN

WSS

ECU
IV

OV

BV

PS

4
11

37
F

RLV
3

33

52

EBS - Gen. 2

Single channel
(wheel)
modulator brake applied

In the illustration above, the ignition is on so the modulator

has power. The footbrake pedal is pressed. The
potentiometers have signalled driver demand to the EBS
ECU, and a pressure signal has been calculated and sent
to the modulator ECU.
IV is energised and is open.
BV is energised and is closed.
OV is not energised and is closed.
RLV now has a pressure signal from IV, so the required
pressure is delivered to the brake chamber, and sensed by
PS.

53

EBS - Gen. 2

PS
WSS

LWS

CAN

WSS

ECU
OV

IV
BV

PS

4
11

37
F

RLV

33

54

EBS - Gen. 2

Single channel
(wheel)
modulator back-up

If the electronic control system fails, the modulators operate

in back-up mode.
Air pressure from the footbrake valve is fed to the back-up
valve (BV) and relay valve (RLV).
Braking force is now controlled by the driver.

55

EBS - Gen. 2
10
WSS LWS1/3 LSV1(2) WSS

WSS LWS2/4 CAN

WSS

ECU
OV

BU
PS
21

33

IV

BV

37
BV

RLV

IV

RLV
F

OV

PS

22

33
12

56

EBS - Gen. 2
Twin channel
(axle) modulator

BV. Back-up valve

IV. Inlet valve
OV. Outlet valve
PS. Brake line pressure sensor
RLV. Relay valve
F. Filter
BU. Back-up air supply

WSS. Speed sensor signal

LWS. Wear sensor signal
CAN. CAN + voltage supply
12. Air tank
33. Brake chamber
37. Modulator

Rear axles each have a twin channel modulator, which

is basically two single channel modulators in a common
housing.
Operation of each channel of the twin channel modulator is
identical to that of the single channel modulator.

57

EBS - Gen. 2

CAN

ECU
IV

BV
41
13

PS

F
DV

43
42

OV

RLV

21

22

37b

58

EBS - Gen. 2
Trailer modulator

BV. Back-up valve

IV. Inlet valve
OV. Outlet valve
DV. Dump valve
RLV. Relay valve
PS. Brake line pressure sensor
F. Filter
CAN. CAN + voltage supply

13. Park brake air tank

21. Trailer supply line
22. Trailer control line
37b. Trailer modulator
41. Service brake front circuit
42. Service brake rear circuit
43. Park brake circuit

The trailer brake modulator is used with trailers which do

not have an EBS brake system. The modulator supplies
compressed air to the trailer brake system, and controls the
trailer brake pressure.
Like the other modulators the trailer modulator is normally
controlled by the EBS ECU, and it also has a back-up function.
Note the additional air supply from the park brake hand control
valve to port 43. The park brake function operates in the same
way as a conventional trailer brake control valve.

59

EBS - Gen. 2

Automatic brake
adaptation Brake
Compatibility
System (BCS)

Automatic brake adaptation ensures optimum brake force

distribution between tractor and trailer. This results in more
stable braking and more even lining wear.
The modulator can adjust the trailer brake pressure + 1.5
bar to - 0.5 bar in relation to the tractor brake pressure.
These pressures cannot be altered.
Adjustment takes place automatically when the vehicle is
moving.

Modulator repair

Limited overhaul of the modulators is possible using repair

kits - refer to IMPACT for parts and repair information.

60

61

EBS - Gen. 2

62

EBS - Gen. 2
Load sensing

The EBS system does not have a load sensing valve.

Because the pressure in the rear axle air bags varies as
vehicle load varies, this pressure is used as a reference for
vehicle load.
A sensor, in the Electronically Controlled Suspension
(ECS) system, detects the varying pressure, and sends a
variable voltage signal to the ECS ECU.
The EBS ECU can read this signal via the data link.
The signal is used by the ECU to calculate the required
brake force, and distribution between the front and rear
wheels.

63

EBS - Gen. 2

64

EBS - Gen. 2

Traction Control
System (TCS)

Terrain TCS

The relative speed of all road wheels is constantly

monitored by the EBS ECU.
If a drive wheel loses grip and starts to spin, the sudden
increase in speed, relative to non drive wheels, is detected.
At road speeds less than 40km/h, engine power is reduced,
and the brake on the spinning wheel is applied, and traction
is transferred to the non spinning drive wheel.
At road speeds above 40km/h only engine power is
reduced.
In certain conditions - e.g. deep clay or snow - it may help
to get the vehicle moving by allowing a certain amount of
wheel spin.
If the TCS switch is pressed, the reference speed at which
traction control starts, is increased by 10 km/h.

65

EBS - Gen. 2

66

EBS - Gen. 2
Trailer Brake
System (TBS)

At certain times - e.g. when changing a trailer, or making

adjustments to the fth wheel - it may be necessary to
independently apply the trailer brakes.
Providing that road speed is less than 4 km/h, pressing
- and holding down - the switch, supplies air at 4 bar
pressure via the trailer yellow line.
When the switch is released, or if road speed is above 7
km/h, the air supply pressure is reduced to zero.

67

EBS - Gen. 2

68

EBS - Gen. 2

Differential lock
function

The Diff. lock function is provided to make it easier to

engage the differential lock, and to prevent damage to
differential components.
When the switch is pressed, the TCS system applies a
combination of engine power reduction and braking, to
synchronise the speeds of the driving wheels, at which
point, the diff. lock will engage.
Note: speed synchronisation will not occur if the Terrain
TCS switch is pressed.

69

EBS - Gen. 2

9990131 - optional
9998603/2

9998699 - 62 pin

70

EBS - Gen. 2
Test equipment

The break-out box, template and harness shown above are

required for the following EBS Gen. 2 checks:

Footbrake valve
- course Task 2

- footbrake signal
- footbrake pressure

- check list (C)

- check list (C)

Harness extension 9990062 is also required.

Modulator course
Tasks 3 & 4

- modulator signal
- modulator pressure

- check list (B)

Turn template 9998603 to the correct side by matching the

plug and template colours.
Note: Harness 9998603 - 7 plugs - can be used on Gen. 2
systems.
Harness extension 9990062 is also required.

71

EBS - Gen. 2
X1 = EBA - BLACK
X2 = EBB - YELLOW
X3 = EBC - GREEN
X4 = EBD - PURPLE

9998596/2
9998699

72

EBS - Gen. 2
Test equipment
ECU course Task 5,
check list - ECU

Harness 9998596/2, with 5 connectors, can be used for

Gen. 2 and Gen. 3 systems.
For Gen. 2 systems, the blue connector is not used.
Earlier harness 9998596, with 4 connectors, can be used
only for Gen. 2 systems.
Harness extension 9990062 is also required.
Break-out box 9998699 is used with harness 9998596/2 for
Gen. 2 systems only.
Note: The check list also refers to break-out box template
9990131, but some of the pin references do not match.
Therefore, use the break-out box pin references

73

EBS - Gen. 2

74

EBS - Gen. 2
VCADS Pro - EBS
Gen. 2 tests course Task 5a

50006-6 brake pads

50012-6 footbrake valve
50011-6 modulators
59364-2 ECU input/output signals
50013-6 TCS function shut off
50020-6 wheel speed sensor
59902-2 ABS control auxiliary brakes
50007-7 lining wear sensor calibration - front axle
50018-7 lining wear sensor calibration - rear axle

75

EBS - Gen. 2

9998544

9998534

ABS

ABS

ABS

76

EBS - Gen. 2
Truck/trailer ABS
- warning lights
and symbols

1 - truck ABS fault

2 - trailer ABS fault
3 - trailer without ABS connected
Note: On trucks pre. version 2, trailer connection is sensed
via the brake light connection - main suzie (77) pin 4.
If current is sensed, via trailer relay (3023), a trailer is
connected.
On version 2 trucks, trailer connection is detected via the
Light Control Module (LCM).

ABS course Task 6,

Harness 9998534 is used to check the trailer modulator on

Gen. 2 trucks.
Harness 9998544 is used to check the ABS trailer info.
relay on pre-98 trucks.

77

EBS - Gen. 2
VCADS Pro - ABS

59305-6 solenoid control valves

59306-6 ECU
59302-6 wheel speed sensor
59303-6 toothed wheel

78

Electronic Braking System - Generation 3

79

EBS - Gen. 3
1

6x2
Tag

6x2
Pusher

6x4

8x2

Gen. 3 Axle congurations

8x4

80

EBS - Gen. 3

Axle
conguration
Gen. 3

Service information in IMPACT refers to the axles, and to

components attached to the axles.
The references are different from those used for Gen.2.
They are simply numbered from 1 to 4, front to rear.

81

82

EBS - Gen. 3
EBS Gen. 3
introduction
Main differences
between Gen. 2
and Gen. 3

EBS Generation 3 was introduced late 2003.

- modulators
- ECU plugs
- ABS valves added (certain axle congurations)
- axle congurations
- wake-up function
- hill start aid
- automatic diff. lock
- new test equipment

Main software changes:

- emergency brake assistance (EBA)

- drag torque control

83

Function

Truck variant Axle cong. Standard

FM/FH
package
EBS-STD

Electronic Stability

Tractors only

Program - ESP

Comfort
package
EBS-MED

4x2,6x2,6x4

ESP
package
EBS-HIG
X

with air susp.

Hill start aid

All

All

Auto. diff. lock

All

Single drive

4x2,6x2
Lining wear trend anal.

All

All

Drag torque control

I-shift

All

Brake assist

All

All

Wheel brake monitor

All

All

EBS status recorder

All

All

84

Function

Truck variant Axle cong. Standard

FM/FH
package
EBS-STD

Comfort
package
EBS-MED

ESP
package
EBS-HIG

Anti Lock Brakes

All

All

Diagnosis via J1587

All

All

Traction Control

All

All

External Brake Demand

All

All

Differential lock

All

All

Brake Blending

All with

All

stalk control
Lining Wear Sensing

All

All

Lining Wear Control

All

All

Brake temperature
warning

All

All

85

EBS - Gen. 3

Software - 3
levels

The chart on the previous pages shows the features

available with the three software levels - Standard, Medium
and High.

Electronic
Stability Program
- ESP

ESP is aimed at helping to stabilise the vehicle if it reaches

an unsafe situation - e.g. skidding, over/understeer, too fast
into a curve, possible risk of vehicle over-turning.
The system uses two additional sensors:
- steering angle sensor on the steering column. This
sensors detects the angle, direction and rate of steering
wheel movement.
- yaw rate sensor, which senses vehicle rotation and lateral
acceleration.
In response to signals from these sensors, ESP attempts
to stabilise the vehicle by applying a combination of engine
power reduction, and braking of certain wheels depending
on the forces detected.

86

EBS - Gen. 3
Electronic
Stability Program
- ESP

Large steering wheel movements at high speed, a load with

high or unstable centre of gravity, can bring the vehicle to
the point of over-turn.
The rst attempted correction is reduction of engine power
to reduce the lateral force.
ESP then attempts to detect if one or more tyres is losing
contact with the road.
ESP detects this by lightly applying the brakes on one of
the inner wheels.
If light braking results in sudden deceleration of the wheel,
this is interpreted as loss of road contact, and all brakes are
applied.
Note: This function does not apply if the trailer is not tted
with EBS.
ESP does not work if there is an EBS fault.

87

EBS - Gen. 3

88

EBS - Gen. 3
Hill Start Aid

Hill start aid helps the driver to move off from a standstill on
a hill.
When the switch is pressed brake release is delayed,
giving the driver more time to operate the throttle and
clutch.
Manual gearbox - brake pressure is maintained until the
clutch is released, or until a certain engine load is detected.
Automatic gearbox - brake pressure is maintained for
a short time after the brake pedal is released, or until a
certain engine load is detected.

89

EBS - Gen. 3
O = no diff. lock
1 = auto. diff. lock
2 = manual diff. lock

90

EBS - Gen. 3
Automatic diff.
lock

This function is available only on trucks with one drive axle.

The diff. lock is automatically engaged if the drive wheels
begin to rotate at different speeds. EBS rst synchronises
the wheel speeds.
The road speed must be less than 15km/h

91

EBS - Gen. 3

CHECK
BRAKES
Status Recorder
92

EBS - Gen. 3

Status recorder

The status recorder records the number of times a function

has been applied - ABS, TCS, EBA, ESP, Temp. alert.
Learning parameters must be reset to erase the fault
codes.

Emergency Brake
Assist (EBA)

If the brake pedal is pressed rapidly, this is interpreted as

an emergency brake situation.
The EBS ECU pressure signals to the modulator ECU are
modied to provide increased brake pressure, so maximum
braking power is attained more quickly.

Drag torque
control

If the EBS system senses that the drive wheel speed is

being retarded too much by the engine brake or retarder,
the EBS ECU sends a signal to the engine brake or
retarder to reduce retardation.

93

EBS - Gen. 3
4
3
1
2

5V
SM2
AGNI
SM1

6
11
12

21
22
94

EBS - Gen. 3

Wake-up signal

The EBS ECU receives a constant supply from the battery.

Whenever the footbrake is pressed - even if the startkey is
at off position - a signal is sent from terminal (6) to the EBS
ECU, and the complete EBS system is switched on.
This ensures that EBS will not go into back-up mode if
other systems fail.
Note: Wake-up does not work if the battery master switch
is off.
5V. Controlled voltage supply to potentiometers
SM2. Pot. output signal - 4.5v - 0.5V
AGNI. Common earth
SM1. Pot. output signal - 0.5V - 4.5V
6. Wake-up signal
11. Front circuit inlet - 8.5 bar
12. Rear circuit inlet - 8.5 bar
21. To front circuit
22. To rear circuit

95

EBS - Gen. 3

Brake
temperature
warning

Brake Blending
- BBF

Brake lining temperature is estimated by the EBS system.

If any wheel brake begins to overheat a warning light is lit.
Overheat also causes brake fade when the braking effect
deteriorates, so the brake pedal must be pressed harder.

BBF is tted only to vehicles with a retarder control stalk

- stalk at Automatic position.
BBF automatically blends braking power provided by
the wheel brakes, and power provided by auxiliary brake
systems - i.e. engine brake (VEB) and/or retarder.
Because the reaction from auxiliary brake systems is
slower than that from wheel brakes, the wheel brakes are
always applied rst.
The ratio of braking power between tractor and trailer is not
affected.
96

EBS - Gen. 3

Wheel brake
monitoring

!
Load sensing

The EBS system constantly monitors the efciency of all

wheel brakes.
If the braking efciency on any wheel brake is less than that
at other wheels - e.g. due to grease on the linings, lining
glazing or sticking calliper - a warning light is lit.
Unlike Gen. 2 where load is sensed only by measuring
the pressure in the rear air bags, with Gen. 3, load is also
sensed by measuring the acceleration achieved for a given
throttle opening, and deceleration achieved for a given
brake pressure,
After two or three gear shifts and brake applications, the
effect of the load has been calculated, and brake pressure
is adjusted accordingly.
Following a load change, and before the load effect has
been recalculated, the rst brake application may feel
different
97

EBS - Gen. 3
External Brake
Demand - EBD

EBD is a demand, via the data link, from another ECU to

apply or release the brakes.
Examples are:
- trailer
- radar
- driver falling asleep detection

98

EBS - Gen. 3

Brake force
distribution - slip
control

To ensure maximum retardation and stability at all times,

the EBS system distributes braking force between front and
rear tractor axles, and between tractor and trailer.

Distribution
tractor front/rear

During light braking, the tractor front and rear axles receive
approximately equal braking force, so lining wear is even.
When more retardation is required, optimum brake force
distribution is achieved by slip-control, whereby braking
force is distributed so that the front and rear wheel rotation
speed is equalised.
If the speed sensors detect that rotation speed is not equal,
braking force to the faster wheels is increased, and braking
force to the slower wheels is reduced.
In relation to the tractor brake pressure, pressure to the
trailer can be adjusted + 1.5 bar to - 0.5 bar.
If the trailer has EBS, all tractor and trailer wheels are
braked using slip-control.

Distribution
tractor /trailer

99

EBS - Gen. 3

X4 - EBD - Green
X3 - EBC - Purple
X2 - EBB - Grey
X1 - EBA - Black
100

EBS - Gen. 3
EBS ECU

The Gen. 3 ECU still has four plugs, but the colours are
different from Gen. 2.

101

EBS - Gen. 3

3
102

EBS - Gen. 3
Modulators

The new modulators, used with Gen. 3 systems, are

smaller then those used with Gen. 2 systems.
The principle of operation is the same.
1. Single channel modulator
2. Twin channel modulator
3. Trailer modulator

103

EBS - Gen. 3

10
9

6b
6
6a
4
5
7a
7

8
7b

10
3

104

EBS - Gen. 3
ABS control
valve

Normal braking

On 4 x 2, 6 x 2 and 6 x 4 trucks, with single front axle, a

single channel modulator, with two ABS, valves is tted.
The ABS valves are controlled by the modulator.
1. Air supply
2. Air delivery
3. Exhaust
4. Inlet solenoid
5. Exhaust solenoid
6. Inlet valve
6a. Exhaust seal on inlet valve
6b. Inlet seal on inlet valve

7. Exhaust valve
7a. Inlet seal on exhaust valve
7b. Exhaust seal on exhaust valve
8. Diaphragm - exhaust
9. Diaphragm - inlet
10. Springs

During normal braking:

- solenoid (4) is not energised, so inlet valve (6) is open.
- solenoid (5) is not energised, so exhaust valve (7) is
closed.
Air can ow freely back and forth through inlet (1) and
delivery (2).

105

EBS - Gen. 3

10
9

1
6b
6
6a
4

5
7a
7

7b

10
3

106

EBS - Gen. 3
ABS control
valve
Lock-up detected

If a tyre begins to lose grip, on loose or icy surfaces,

braking will cause that wheel to lose speed at a faster rate
than other wheels. Without correction the wheel will soon
lock-up, and cause loss of control.
The speed difference is detected by the wheel speed
sensor, so an ECU signal results in:
- solenoid (4) is energised, so inlet valve (6) is closed.
- solenoid (5) is energised, so exhaust valve (7) is open.
The pressure to the brake chamber for the locking wheel is
reduced, and wheel lock-up is avoided.

107

EBS - Gen. 3

10
9

6b
6
6a
4
5
7a
7

8
7b

10
3

108

EBS - Gen. 3
ABS control
valve
Wheel speed
equalised

When the sensors detect that all wheels are rotating at

the same speed, the valve switches to pressure maintain
mode:
- solenoid (4) is energised, so inlet valve (6) is closed.
- solenoid (5) is not energised, so exhaust valve (7) is
closed.
This ensures that the braking pressure is maintained in
the chamber, at a level which gives the maximum possible
retardation, whilst avoiding wheel lock-up.
Any further pressure applied to the footbrake pedal, has no
effect on the air pressure in the chamber.

109

EBS - Gen. 3
Multi-channel
systems

Depending on the number and conguration of axles, EBS

systems have 3, 4 or 5 channels.
The number of channels refers to the total number of
modulator channels - excluding the trailer modulator:

3 channel

1 x single channel modulator + 1 x 2 channel modulator.

4 channel

2 x single channel modulator + 1 x 2 channel modulator.

5 channel

3 x single channel modulator + 1 x 2 channel modulator

110

111

EBS - Gen. 3
10

36

10. Footbrake valve

33. Brake chamber
36. ABS valves
37. Single channel modulator
37a. Twin channel modulator
37b. Trailer modulator

36

CAN J1936
CAN
J1939

ECU
37
E

37a
AG

37b

AG. To auto. gearbox

E. To engine
ECU. EBS ECU
R. To retarder
T. To trailer
SS. Wheel speed sensor
WS. Wear sensor
J1708/1587. Slow data link
(orange)
J1939. Fast data link (green)
J1936 -

CANJ1708/1587

112

EBS - Gen. 3
WS

SS

33

36

10

37

WS

SS

33

33
ECU

36

SS

WS

37a
T

33

SS

WS

37b

Note:

Three Channel System - 4 x 2

2 ABS valves for front axle

Front single modulator controls - axle 1, LH and RH
Rear 2 channel modulator controls - axle 2 LH and RH

113

EBS - Gen. 3
10

36

10. Footbrake valve

33. Brake chamber
36. ABS valves
37. Single channel modulator
37a. Twin channel modulator
37b. Trailer modulator

36

CAN J1936
CAN
J1939

ECU
37
E

37a
AG

37b

AG. To auto. gearbox

E. To engine
ECU. EBS ECU
R. Retarder
T. To trailer
SS. Wheel speed sensor
WS. Wear sensor
J1708/1587. Slow data link
(orange)
J1939. Fast data link (green)
J1936 -

CANJ1708/1587

114

EBS - Gen. 3
WS

SS

10

36

33

33
37

WS

SS

Note:

WS

ECU

33
36

SS

WS

37a

33

SS

WS

SS

WS

37b

Three Channel System - 6 x 4

2 ABS valves for front axle

Front single modulator controls - axle 1, LH and RH
Rear 2 channel modulator controls - axle 2 and 3, LH - axle 2 and 3, RH

115

EBS - Gen. 3

10

36

10. Footbrake valve

33. Brake chamber
36. ABS valves
37. Single channel
modulator
37a. Twin channel
modulator
37b. Trailer modulator

36

CAN J1936

37b

37

ECU

CAN
J1939

37

AG

37a
CANJ1708/1587

AG. To auto. gearbox

E. To engine
ECU. EBS ECU
R. To retarder
T. To trailer
SS. Wheel speed sensor
WS. Wear sensor
J1708/1587. Slow data
link (orange)
J1939. Fast data link
(green)
J1936.

116

EBS - Gen. 3
WS

36
SS

10
33

33
37

WS

SS

Note:

36

37

ECU

33

WS
SS 33

SS

WS

37a

33

SS

33

WS

SS

WS

37b

Four Channel System - 6 x 2 pusher

2 ABS valves for front axle

Front single modulator controls - axle 1, LH and RH
Rear 2 channel modulator controls - axle 3, LH and RH
Rear single channel modulator controls - axle 2, LH and RH

117

EBS - Gen. 3

10. Footbrake valve

33. Brake chamber
36. ABS valves
37. Single channel
modulator
37a. Twin channel
modulator
37b. Trailer modulator

10
CAN J1936

37b

37

ECU

CAN
J1939

37
E

AG

37a
CANJ1708/1587

AG. To auto. gearbox

E. To engine
ECU. EBS ECU
R. To retarder
T. To trailer
SS. Wheel speed sensor
WS. Wear sensor
J1708/1587. Slow data
link (orange)
J1939. Fast data link
(green)
J1936.

118

EBS - Gen. 3
WS

SS

33

10
33

33

37

SS

33

WS

ECU

37
WS

SS

SS

WS

37a

33

33

33

SS

WS

33

SS

WS

37b
Note:

Four Channel System - 8 x 4

No ABS valves
Front single modulators control - axle 1 and 2, LH - axle 1 and 2, RH.
Rear 2 channel modulator controls - axle 3 and 4, LH - axle 3 and 4, RH.
An 8 x 4 is the front of an 8 x 2, and the rear of a 6 x4

119

EBS - Gen. 3

10

37b
CAN J1936

ECU
37

37
CAN
J1939

10. Footbrake valve

33. Brake chamber
36. ABS valves
37. Single channel
modulator
37a. Twin channel
modulator
37b. Trailer modulator

AG

37

37a
CANJ1708/1587

AG. To auto. gearbox

E. To engine
ECU. EBS ECU
R. To retarder
T. To trailer
SS. Wheel speed sensor
WS. Wear sensor
J1708/1587. Slow data
link (orange)
J1939. Fast data link
(green)
J1936.

120

EBS - Gen. 3
WS

SS

33

10

37

WS

Note:

33

SS

ECU
T

33

33

SS

33

SS

WS

WS

37

37a

37
SS

33

33

33

SS

WS

WS

37b

Five Channel System - 8 x 2

No ABS valves
Front single modulators control - axle 1 and 2, LH - axle 1 and 2, RH
Rear single modulator controls - axle 4 LH and RH
Rear 2 channel modulator controls - axle 3 LH and RH

121

EBS - Gen. 3

A
9998699 - 62 pin
9990180

122

EBS - Gen. 3
Footbrake valve
test

For the footbrake valve test, use harness 9990180, breakout box 9998699, and harness extension 9990062.
Note: The large plug (A) is the correct plug to use when
connecting to the footbrake valve.

123

EBS - Gen. 3

9990221

9990180
9998699 - 62 pin

124

EBS - Gen. 3
Modulator test

For the modulator test, use harness 9990180, breakout box 9998699, break-out box template 9990221 and
harness extension 9990062.
Note: Lead No. 2 - 4 pin is used only for ESP.

125

EBS - Gen. 3

9998567
126

EBS - Gen. 3
Trailer modulator
test

For the trailer modulator test, use harness 9998567.

127

EBS - Gen. 3

9998539

9998539
X1 BLACK

9998596/2

X2

GREY

X4

PURPLE

X3

GREEN

9998596/2

9998699 - 62 pin 128

EBS - Gen. 3
ECU test

Refer to the check list - EBS Gen. 3 ECU.

For the ECU test, use harness 9998596/2 (Gen. 2
harness). Tie-up the blue plug - it is used only for ESP.
Because Gen. 3 ECU connector X2 is different from
Gen. 2, new harness 9998539 is also required.
Break-out box 9998699 is used without template 9990221.
Harness extension 9990062 will be required.

129

EBS - Gen. 3
Op. Ref. No.

Reset test

Function

59392-2
59393-2
59394-2

1
2a
2b

59395-2
59396-2

3
4

Brake pedal activation

Wheel speed
Wheel speed
(changed tyre circumference*)
Manoeuvrability
Control unit reset

* If new wheels or tyres are tted, resulting in a different tyre

circumference, this parameter must be reset.

130

EBS - Gen. 3
Resetting
learning
parameters

In addition to recording fault codes, the EBS ECU also

records other information - e.g. braking characteristics,
number of activations of components, change of wheel/tyre
diameter.
Such information is referred to as learning parameters.
Using the instrument panel display control stalk - or VCADS
Pro - most fault codes can easily be deleted without going
through any other procedure.
However, when certain fault codes have been recorded a
number of times, any related learning parameter must be
reset before the fault code can be deleted.
The table above gives the operation numbers for the ve
reset tests.
For reset procedure, refer to these numbers in IMPACT.

131

132

133

134