Audi drive select
setting

677_023
21

The system principle is illustrated using the example of
driving over a bump (“positive” obstacle) with the left front
wheel. The aim of the regulating activities is to calm the
vehicle body as far as necessary to achieve the best possible
compromise between driving comfort and dynamics.
Dynamics and comfort are weighted on the basis of the
Audi drive select setting chosen by the driver.
› When the bump is reached, the vehicle body experiences
vertical acceleration (z direction) at the front axle/above
the left front wheel. This vertical acceleration is measured by the sensors in Drivetrain Control Module J775.
In addition, the suspension at the left front wheel may
compress slightly. This is also detected by the allocated
vehicle level sender. Alongside a large amount of additional information (for example, vehicle speed, lateral
acceleration etc.), this information is evaluated by J775.
J775 proceeds to reduce the damping force of the left
front damper in the compression stage. At the same
time, the control module determines how much the
tension of the torsion bars of the actuators on the front
axle (stabilization rate) needs to be reduced by to calm
the vehicle body accordingly. The control module calculates the changes to the angles of rotation of the actuators required to do so and requests that this be implemented by chassis Suspension Stabilization Control
Module 1 J1152 on the front axle.

677_022

› The lower damping force and stabilization rate allows
for suitably large spring deflection on the front wheel.
The vertical forces applied to the vehicle body are
thereby reduced. The acceleration of the vehicle body
is restricted to a level which is comfortable for the
occupants.
› When the rear axle reaches the bump, the dampers
and actuators on the rear axle go through the same
processes as those specified above.

Right Front Level
Control System Sensor
G289

Suspension Stabilization
Control Module 1 J1152

Drivetrain Control Module
J775

Actuator

Left Front Level
Control System Sensor
G78
677_024

22

Additional preview function
Additional functions
In addition to the basic functions, additional functions can
be achieved by the active suspension.
One function makes use of the option to detect certain
irregularities in the road surface in advance. This is achieved
by evaluating the optical signals from Driver Assistance
Systems Front Camera R242. Driver Assistance Systems
Control Module J1121 evaluates the camera data according
to defined criteria. It determines the height and, on that
basis, the type of obstacle. Typical obstacle types include
harmonic bumps and speed bumps. Smaller road
irregularities (potholes) are usually not detected due to
their “edges” being on the same level as the road itself.
Drivetrain Control Module J775 also receives information
about the resolution quality from Driver Assistance
Systems Control Module J1121 to assist it with the
analysis.

On the basis of this information, J775 decides on the
relevance of regulating and the ongoing procedure. Driver
Assistance Systems Control Module J1121 provides
Drivetrain Control Module J775 with current data
approximately 18 times per second.
The main benefit of the preview function is the option of
initiating corresponding measures in advance. The basic
function can only be activated when measured values
from the relevant sensors show that the vehicle has
already begun driving over the obstacle. With the preview
function, the counter-measures have already been
initiated when the front wheels reach the obstacle. The
function is active at speeds of up to approximately 37.28
mph (60 km/h). The preview function has the following
regulating components:

677_025

Pro lift

Pro comp

When the vehicle drives over a “positive” obstacle (for
example, speed bump, see image), the vehicle’s suspension
compresses. Vehicle occupants find it particularly uncomfortable if the entire spring travel is used during spring
deflection. If the preview function detects a “positive”
obstacle, pro lift initiates a corresponding activation of the
actuators. The vehicle body is raised early so that there is
sufficient spring travel available when the vehicle drives
over the obstacle. As a result, it is possible for the vehicle
to be raised by up to 1.57 in (40 mm) before it reaches the
obstacle, depending on the type of obstacle detected. This
occurs gently and is hardly noticeable for the driver.

Almost exactly at the same time that the relevant wheel
“arrives” at the obstacle, this regulating component initiates a further regulation to follow the contour of the obstacle. This actively moves the wheel towards the vehicle body
by activating the relevant actuator. This corresponds to a
spring travel movement. Thanks to pro lift, it has already
been ensured that sufficient spring travel reserves are available. The aim is to eliminate (or at least significantly
reduce) the impulse caused by the ramp-shaped contour of
the obstacle at the moment when it first makes contact
with the wheel. As part of this, the damping forces are also
adjusted accordingly. A similar process occurs when the
vehicle is moving off the obstacle. In this case, the wheel’s
suspension is actively extended so that it can follow the
contour of the road closely as possible.

23

677_026

An obstacle is detected by evaluating the camera data. It is classified as a “positive” obstacle (protruding from the road
surface). For this type of obstacle, the highest level of spring travel possible must be made available. Drivetrain Control
Module J775 calculates the specified angle for the lever and requests that Suspension Stabilization Control Modules 1 and 2
implement this. The vehicle body is raised accordingly before the wheel reaches the obstacle. The spring travel available is
thereby increased by up to 1.57 in (40 mm).

677_027

Immediately before the calculated moment that the vehicle arrives at the obstacle, Drivetrain Control Module J775 triggers
the process to raise the wheel affected. This avoids hard contact with the obstacle.

677_028

“Leaving” the obstacle is supported by adjusting the vertical movement of the wheel to the contour of the obstacle. The
extension of the springs is supported, if necessary, by the active activation of the actuator.
24

Additional crash lifting function
Despite many protective systems, injury to the occupants cannot be ruled out in the event of a traffic accident. Side collisions
also constitute a certain injury risk for the vehicle occupants affected. The main cause of this is the relatively small space for
deformation between the vehicle occupants on the side of the collision and the exterior of the vehicle. The structural elements
in-between must absorb the kinetic energy of the colliding vehicle.
Depending on the force of the impact, the structural elements may deform in the direction of the vehicle interior (intrusion).

Side collision without crash lifting function

677_029

Side collision with crash lifting function

677_030

The area surrounding the side of the vehicle is monitored by four corner radar sensors, which are also required for Audi pre
sense side. Driver Assistance Systems Control Module J1121 evaluates these data.
Depending on the situation, it determines the potential risk posed by a vehicle approaching from the side. It calculates the
criticality (a numerical figure which represents the potential risk from the approaching vehicle) and the expected time until
the collision. This information is sent to the Airbag Control Module J234 which initiates the following actions if necessary
(pre sense side cascade). As part of this, Drivetrain Control Module J775 is requested to raise the vehicle for a collision.
If the relevant object/vehicle is no longer in the detection area, the request is canceled by the Airbag Control Module and
the vehicle is returned to its original level.
If the less common case occurs in which a vehicle on a collision course swerves away, the vehicle is lowered again after a
defined period of time. The collision function is also active in towing mode, with unchanged parameters.
For the collision function to be activated when necessary, all doors, the trunk and hood lids must be closed, Terminal 15
must be activated and the vehicle must have exceeded a speed of 4.9 mph (8 km/h) once. The function is no longer active
when a door is opened or Terminal 15 is switched off. The collision function is also deactivated if ESC and/or pre sense is
deactivated.

25

Additional elevated entry function
This optional function raises the vehicle body when a door is opened. The vehicle is raised approximately 1.57 in (40 mm)
(compared to the reference level in Audi drive select mode “auto” or “comfort”) in approximately one second.
The original level is reset:
› Approximately 10 seconds after all four doors have been closed.
› When the vehicle starts moving.
› When the vehicle is locked.
› When the Audi drive select mode is changed.
› When the engine is switched off and the door is open, after a defined period to retain the battery charge level.
The raised condition is displayed in the MMI touch screen.

677_032

Additional corner tilting function
This function is only activated if the comfort+ mode is chosen in Audi drive select.
Because of the centrifugal forces acting on the vehicle body in corners, the body tilts towards the outside in corners. This
undesired (from the perspective of driving dynamics and comfort) roll is reduced by the active damping control or largely
neutralized if the vehicle is equipped with electromechanical roll stabilization.
The active suspension regulates in a more engaged manner in corners because it actually tends to tilt the vehicle body in the
opposite direction. This is done by lowering the body on the inside of the corner and raising it on the outside. This causes the
vehicle to tilt up to approximately 3° into the corner and achieves even more effective support via the wheels on the outside of
the corner. At the same time, a significant improvement in comfort for the vehicle occupants is achieved as the lateral forces
acting on them are reduced.
The regulating software mainly evaluates the vehicle speed and the lateral acceleration transmitted by the Airbag Control
Module.
Key
Vehicle body tilt in corners
caused by the centrifugal force
acting on the vehicle’s center of
gravity
Vehicle body tilt in corners
caused by the active suspension

26
677_033

Additional helicopter function
Forces also act on the vehicle body when undergoing
longitudinal acceleration (forward propulsion or braking).
When the vehicle accelerates, the body supports itself on the
wheels of the rear axle due to the effect of the inertial force;
the load on the front axle is reduced. As a result, the rear axle
suspension deflects and the front axle suspension extends.
When the vehicle is braking, the inertial force works in the
opposite direction; the suspension deflects at the front axle
and extends at the rear axle. On vehicles with damping
control, these pitching movements are counteracted by
adjusting the damping forces.

The regulating function of the active suspension also works
to compensate for the effects of these dynamic driving
situations. Under braking, the front axle is not only prevented from dipping forward, but the body is actually raised
slightly at the front.
When the vehicle accelerates, the system regulates in the
opposite direction and causes the body to be lowered (suspension compressed) at the front axle and the suspension to
be extended at the rear axle.
This raising/lowering is mostly unnoticeable for the vehicle
occupants. What can be noticed, however, is increased
seating comfort thanks to the reduction of longitudinal
forces acting on the occupants in or against the direction of
travel.

677_035

Raising the vehicle at the front axle and lowering it at the rear axle under braking counteracts the inertial force and enables
significant comfort improvements by reducing the longitudinal forces acting on the occupants.

677_034

When the vehicle is accelerating, the body is lowered at the front axle and raised at the rear axle. A significant improvement in
comfort due to a reduction in the longitudinal forces acting on the occupants is also the result here.

27

Operation and servicing
Operation and driver information
The driver cannot deactivate the basic functions of the active
suspension, but can directly influence the regulation through
Audi drive select. The driver also has the option of being
informed of the status of the function while the system is
actively regulating. To do this, the menu option “Active
suspension” must be selected (Car – Vehicle info – Active
suspension). The display shows, for each wheel individually,
to what extent the movements of the vehicle body are being
compensated for. The driver can also choose to what extent
the system should compensate for bumps in the road.

Audi drive
select

Active
Suspension

Efficiency
assist

A/C

Lights & vision

Parking aid

By selecting the sprocket symbol in the active suspension
display, the driver can switch off the unevenness compensation function (preview function) or choose between gentle
and strong unevenness compensation.
The elevated entry function can also be activated or deactivated by the driver. Detailed information on the operation
and displays of the relevant vehicle model can be found in
the Owner’s Manual.

Seats

Driver assist
systems

Car Active suspension

Car Active suspension
Analysis of road ahead: unevenness compensation
Off

Low

High

Elevated entry

677_037

28

System behavior in the event of a fault
Drivetrain Control Module J775 performs a system diagnosis
and reacts accordingly to implausibilities, system faults and
special effects in the immediate surroundings (temperature,
system utilization and electrical load).
The driver may be notified via warning lamps (neutral white,
yellow, red) and a driver message. The warning lamp symbol
is identical to the symbol for the air suspension system. The
driver message indicates whether the notification is about
the air suspension or the active suspension. The various
displays are described in the Owner’s Manual.

677_039

A two-level concept of system degradation has been developed. The aim is to avoid emergency running mode. The first
level involves a relatively small reduction in the power and
torque of the actuators. The negative effects caused to
comfort are, for the most part, not noticeable to the vehicle
occupants. The driver is informed of the activation of the
second level by a white warning lamp and a text in the
display. The reduction in the vehicle’s roll rigidity achieved in
this level approximately corresponds to that of the normal
running gear.

677_040

If an actuator fault is detected, all actuators are switched off
and the dampers are actuated with constant current. This
achieves significant hydraulic damping which allows for
sufficient roll stability with corresponding restrictions in
comfort. The driver is informed of emergency running mode
by the yellow warning lamp and a corresponding text.
677_039

If there is a fault on a damper, the activation of the damping
valves of all dampers is switched off. A damper fault has no
effect on the activation of the actuators. Here, the driver also
receives a fault message via the activation of the yellow
warning lamp and a text on the display.

677_042

677_039

29

If a vehicle level sender fails, the damping valves also receive
constant current and the activation of the actuators is
switched off. As a result, significant damping forces are
achieved on the front and rear axles. The driver is also
informed of this via the yellow warning lamp and a corresponding text.

677_041

677_039

If there is a fault with Drivetrain Control Module J775 which
makes it necessary to switch off the actuators, the air spring
system and the damping control are also affected because
this module is also responsible for regulating these systems.
This condition is shown by the red warning lamp. Because it
is only possible to continue driving the car with restrictions
due to significantly reduced stability, a driver message is
displayed requesting the driver to stop the vehicle.

677_038

677_039

30

Service operations
The following components can be replaced if necessary:
› The entire module, including the control module,
actuators and integrated connector console.
› The wiring harnesses.
› The stone deflector covers for the control motors on the
rear axle.
The Suspension Stabilization Control Modules have the
following Address Words:
› 00D4 - Suspension Stabilization Control Module 1
J1152.
› 00D5 - Suspension Stabilization Control Module 2
J1153.

Basic setting is required for each of these modules after
they have been replaced. This involves allocating the vehicle
ride heights (measured values from vehicle level senders)
at the four wheel positions to the relevant actuator angles
(measured values from the rotor position senders) and
storing this information in the control modules.
The vehicle ride heights were already adapted when Basic
setting of Drivetrain Control Module J775 was performed.
This involved allocating the measured values from the
vehicle level senders to the actual ride heights measured at
the four wheel positions.
Therefore, after successfully performing Basic setting of
control modules J1152 and J1153, intended changes to the
vehicle ride height can be converted directly into the angle
changes required at the actuators/electric motors by the
control modules and also set accordingly.

677_043

The crash lifting function must be deactivated for work in
an inspection pit or on a hoist. This is done by switching off
the ignition (Terminal 15 off) and opening the driver’s door
once. On vehicles with active suspension, the vehicle may
raise or lower itself via the elevated entry function when
the ignition is switched off. This function must also be
deactivated. For information on this, please refer to the
Owner’s Manual.
The active suspension actuators operate at 48V. It is
required that the system be de-energized before performing relevant removal/installation procedures. Follow all
work steps and sequences specified in ElsaPro.

System behavior in Shipping Mode
Regulation remains active in Shipping Mode. However, the
elevated entry function is deactivated. This prevents the
vehicle’s ride height from being raised when a door is
unlocked/opened. This reduces the possibility of damage to
body panels when vehicles are loaded and unloaded from a
car transporter.
System behavior in Transport Mode
Regulation is deactivated in Transport Mode. This relieves
the load on the electrical system because the battery is not
utilized by the regulating processes.

Note

Caution! Before working on vehicles with active suspension, read and follow all the safety precautions given in
ElsaPro.

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Knowledge assessment
An On-Line Knowledge Assessment (exam) is Available for this eSelf-Study Program.
The Knowledge Assessment is required for Certification credit.
You can find this Knowledge Assessment at: www.accessaudi.com
From the accessaudi.com Homepage:
› Click on the “App Links”
› Click on the “Academy site CRC”

Click on the Course Catalog Search and select 960393B - “Active suspension”.

Please submit any questions or inquiries via the Academy CRC Online Support Form
which is located under the “Support” tab or the “Contact Us” tab of the Academy CRC.

Thank you for reading this eSelf-Study Program and taking the assessment.

32

960393
All rights reserved.
Technical specifications subject to
change without notice.
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2200 Ferdinand Porsche Drive
Herndon, VA 20171