Rear axle

Engine type

2.0l TFSI 252 hp
(188 kw)

Engine type

2.0l TFSI 252 hp
(188 kW)

Minimum wheel size

17“

Minimum wheel size

17“

Brake type

Conti 4MF 42-42
Fixed caliper

Brake type

TRW PC43HE EPBi
floating caliper

Number of pistons

4

Number of pistons

1

Brake disc diameter

13.3 in (338 mm)

Brake disc diameter

12.9 in (330 mm)

Brake disc thickness

1.18 in (30 mm)

Brake disc thickness

0.86 in (22 mm) (ventilated)

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Conti 4MF 42-42

56

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TRW PC43 HE EPBi with ventilated brake disc

Electro-mechanical parking brake (EPB)
The electro-mechanical parking brake is standard equipment for the Audi A4. In terms of design, function, operation and scope of service, the actuator is identical to that
used in the Audi A7 Sportback. The control software is an
integral part of ABS Control Module J104.

Electro-mechanical parking brake (EPB)

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Brake servo and master brake cylinder
A size 8/9“ tandem brake servo with a "single-rate" characteristic is used in the Audi A4. The brake light switch is the
same as the 2017 Q7. It is located on the master brake
cylinder and is a Hall-effect sensor.
Vacuum is supplied by a mechanically powered vacuum
pump.

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57

Electronic Stability Control (ESC)
Two versions of the ESC 9.0 by Robert Bosch GmbH are
used in the Audi A4. Vehicles equipped with ACC have a
six-piston hydraulic pump and three pressure sensors for
additional measurement of the brake pressure within the
brake circuits. A 2-piston hydraulic pump is used in vehicles
without ACC. These ESC units are already used in the 2017
Audi Q7. The control software has been modified for use in
the A4.
The module is located on the left hand side of the engine
compartment under the Engine Control Module. It uses
the measured data (longitudinal and transverse acceleration, yaw rate) provide by the sensors in Airbag Control
Module J234.
Active wheel speed sensors have been adopted from the
2017 Q7. The ESC service operations are identical to those
of the 2016 Audi A7 Sportback or 2017 Audi Q7.

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Operation and driver information
The two-stage operating concept has also been implemented in the Audi A4. Sport mode is activated by briefly
pressing the ESC button (less than three seconds). The TCS
and ESC control functions are limited in order to allow a
more sporty style of driving. If the ESC button is pressed for
longer than three seconds, TCS and ESC are fully deactivated.

Reference
For further information about the design, function and service operations for ESC, please refer to eSelf-Study Program
960163, The 2017 Audi Q7 Running Gear and Suspension System.
58

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Steering system
Overview
Like its predecessor, the Audi A4 is equipped with an electro-mechanical steering system (EPS). The steering column
is mechanically adjustable.

Dynamic steering (not available at model introduction) is
also optional.

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Steering system with dynamic steering option (not available at model introduction).

59

Steering column
The mechanically adjustable steering column is identical in
design and function to that of the 2017 Q7. The modified
installation position and the modified adjustment range
(axial/vertical 2.3/1.9 in (60/50 mm) compared with the
Q7 is achieved by using an adapted bracket and different
stop elements. If the vehicle is equipped with the optional
dynamic steering system, a variant with specially adapted
connection dimensions is used.

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Electro-mechanical steering (EPS)
Design and function
The electro-mechanical steering system in the Audi A4
transmits power to the steering rack through a ball drive
as in the Audi R8.
The ball drive is driven by a belt drive from an electric
motor aligned in parallel with the steering rack. In the
Audi A6, A7 Sportback, A8 and Q7 models, the electric
motor concentrically surrounds the steering rack.

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The paraxial layout was chosen for design space reasons in
particular. The concentric layout involves making allowance for an installation height of about 4.7 in (120 mm),
the installation height for the paraxial layout is only about
2.3 in (60 mm).
The steering ratios for the dynamic electro-mechanical
steering system (not available at model introduction) are
more direct than those of the standard system.

Torsion bar

Steering torque sender

Steering pinion

Ball drive

Electric motor
All-wheel drive

Belt drive

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60

Operation and driver information
This steering system is tailored to the driver by selecting a
mode in the Audi drive select system. Three maps have
been programmed into the control module for this
purpose.
System faults are indicated to the driver by the usual yellow
and red warning symbols. If the maximum steering assistance achievable by the system is less than 60% of the
maximum servo power, the red warning symbol is activated.
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Service operations
The service operations for the steering system used on the
Audi A4 are also identical to those for the systems used on
the Audi A3, A6, A7 Sportback, A8, Q7 and R8 models.
For detailed information, refer to eSelf-Study Program
960143, The 2015 Audi A3 Running Gear and Suspension
System.
It is no longer necessary to program the maximum steering end-stops after replacing the steering. This is performed automatically during subsequent driving cycles. A
basic setting function for resetting the programmed
values allows an existing steering system to be installed
in a different vehicle. The steering unit can only be
replaced as a complete unit. The steering unit in combination with the sub-frame is a key factor in body stiffness.
The instructions given in ElsaPro must be followed when
removing and installing the steering unit.

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Steering wheels
Steering wheel

Equipment
Multi-function steering wheel with
trapezoidal airbag module

Steering wheel

Equipment
Multi-function steering wheel with
round airbag module and flattened
rim (For use in S and S-line models.
Not available at vehicle introduction).

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61

Dynamic steering (not available vehicle introduction)
Dynamic steering is optional for the Audi A4. The Audi A4 is
the first Audi model to be equipped with the second-generation dynamic steering system.

Gear unit

Electric motor

New features of the actuator
The gear ratio (angle of rotation of steering pinion relative
to angle of rotation of electric motor) has been changed
from 1:50 to 1:30. This has increased maximum positioning velocity from approximately 450°/s to approximately
650°/s. Maximum motor speed has also been reduced to
3200 rpm from 4500 rpm. Acoustic response and dynamics
during stabilizing steering inputs have been improved.
The new two-piece housing is about 12.8 oz (400 g) lighter
than that of the first-generation actuator. Dust and water
protection have been improved. The gear housing and
motor housing are completely separate.
The mechanical lock for the hollow shaft of the electric
motor is a new design. A proportional magnet is now used
instead of the "digital" electric magnet. A key advantage is
the elimination of locking noise. Power consumption is also
reduced.

Mechanical lock
Dynamic steering actuator

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New features of the electric motor
Maximum torque has been increased to 1.4 Nm from
1.1 Nm. The rotor position sensor has double the number
of magnetic pole pairs, increasing the sensor resolution to
7.5° from 15°.

Active Steering Control Module J792
The control module uses a dual core microprocessor and
communicates over the FlexRay data bus. A one piece
connector replaces the three individual connectors used in
previous versions.

Service operations
In terms of the service operations, the second-generation
dynamic steering system is identical to the first-generation
system.
If it is necessary to replace the actuator, the steering
column unit must be replaced. However, if it is necessary to
replace the steering column, the intact actuator can be
reused.

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Adaptive Cruise Control (ACC)
The fourth-generation ACC system is used in the Audi A4.
In terms of design and function as well as operation and
service operations, the ACC system of the A4 is identical to
that of the Q7.

The configured time intervals (time gaps) to vehicles ahead
can be varied by the system within certain limits ("flexible
time gaps").

The ACC-based assistance systems first used in the Audi Q7
are also offered for the Audi A4. When adapting these assistance systems for the Audi A4, special attention was given to
efficiency and reducing CO2 emissions.

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Right Adaptive Cruise Control Sensor G259 and
Distance Regulation Control Module J428.

Left Adaptive Cruise Control Sensor G258 and
Distance Regulation Control Module 2 J850.

Reference
For detailed information about the system configuration, the assistance functions, system operation, driver information and
service operations for the ACC, refer to eSelf-Study Program 960163, The 2017 Audi Q7 Running Gear and Suspension
System.
63

Wheels and tires
Premium models come with standard 17” wheels. 18”
wheels are optional. The Premium plus and Prestige models
have 18” wheels as standard.

All models will come equipped with a full-size temporary
space-saving spare tire and jack.

Standard wheels
Premium

Premium plus / Prestige

7.5Jx17 5-parallel spoke design
Cast wheel
95H all season tires

8Jx18 5-spoke dynamic design
245/40 R18 93H all-season tires

Optional wheels
Premium

Premium plus / Prestige

8Jx18 10-spoke design
245/40 R18
93H all-season tire

8.0J x 18 ET40
Flow form cast wheel
Bicolor
245/40 R18 93H all-season tires

Tire Pressure Monitoring System
The second-generation indirect TPMS is standard equipment for the Audi A4. In terms of design and function,
operation and driver information as well as service and
diagnosis functions, the system is identical to the systems
already in use in other current Audi vehicles.

64

Notes

65

Electrical system
Installation locations of control modules
Some of the control modules shown in the overview are
optional and/or country-specific equipment.

Refer to the current service literature for details of control
module installation positions as well as instructions for
installation and removal.

J387

J428

J1023

A27

J794

J844

J685
J500

J217

E380

J587

R242

E87

J764
J898

J285

J527

J623
A31

J792

J104

J1018
J519
J850

J386

Key:
A27
A31

Right LED Headlamp Power Output Module 1
Left LED Headlamp Power Output Module 1

E87 Front A/C Display Control Head
E265 Rear A/C Display Control Head
E380 Multimedia System Control Head
J104
J136
J217
J234
J245
J285

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ABS Control Module
Memory Seat/Steering Column Adjustment Control Module
Transmission Control Module
Airbag Control Module
Power Sunroof Control Module
Instrument Cluster Control Module

J386
J387
J393
J428
J492
J500
J519
J521
J525
J527
J533

Driver Door Control Module
Front Passenger Door Control Module
Comfort System Central Control Module
Distance Regulation Control Module
All Wheel Drive Control Module
Power Steering Control Module
Vehicle Electrical System Control Module 1
Front Passenger Memory Seat Control Module
Digital Sound System Control Module
Steering Column Electronics Control Module
Data Bus On Board Diagnostic Interface

J245

J927
J769

J649

J521

J492

J775

J234

J772

E265

J533

J136

J648

J393
J525

J770

J928
J926

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J587
J623
J648
J649
J685
J764
J769
J770
J772
J775

Selector Lever Sensor System Control Module
Engine Control Module
Left Rear Information Display Control Head Control Module
Right Rear Information Display Control Head Control Module
Front Information Display Control Head
Electronic Steering Column Lock Control Module
Lane Change Assistance Control Module
Lane Change Assistance Control Module 2
Rearview Camera System Control Module
Drivetrain Control Module

J792 Active Steering Control Module
J794 Information Electronics Control Module 1
J844 Automatic High Beam Assist Control Module
J850 Distance Regulation Control Module 2
J898 Windshield Projection Head Up Display Control Module
J926 Driver Side Rear Door Control Module
J927 Passenger Side Rear Door Control Module
J928 Peripheral Camera Control Module
J1018 Left Light Control Module
J1023 Right Light Control Module
R242 Driver Assistance Systems Front Camera

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Topology
For a detailed description of the control modules and the
electrical system, refer to eSelf-Study Program 970563,
The 2017 A4 Electronic and Electrical Systems.

Flap Control
Motors
1 ­– 15

Front A/C Display Control Head
E87

Driver Side Rear Door
Control Module
J926

Driver Door Control
Module
J386

Fresh Air Blower
Control Module
J126