Precise detection of the movement and positions of the gear-shift actuators/selector
forks is of fundamental importance for changing gear and transmission control. It is
imperative to ensure that no prohibited gear-shift positions can occur. The information is
read by Gearbox Control Unit 1 J743 with the aid of 4 travel sensors. Sensor magnets
(permanent magnets) are used as position markers and are attached to each of the gear
shift actuators. See also sensor readings on page 31.
The following gear-shift actuators (selector forks)/gears and readings are assigned to the
4 travel sensors:
››
››
››
››

G487 – for gear-shift actuator A – gears 5/1 – sensor reading IDE02864
G488 – for gear-shift actuator B – gears 2/6 – sensor reading IDE02872
G489 – for gear-shift actuator C – gears 3/7 – sensor reading IDE02880
G490 – for gear-shift actuator D – gears R/4 – sensor reading IDE02888

If one of the travel sensors fails, the gear train subset concerned is deactivated and an
appropriate safe mode program activated.
In order to guarantee the required position detection accuracy, the travel sensors and/or
the selector forks have to be calibrated by means of a Basic Setting. (For example, after
replacing the Mechatronic module).
Parking Lock Sensor G747

Interface module
Parking lock module

G747

Sensor magnet

G747 is used to determine the following positions
(indicated in Measuring value IDE08465 for parking lock
actual status):
Engaged → Intermediate position → Not engaged
Due to tolerances when determining the parking lock position, the intermediate position is indicated when the parking
lock is being held in the P-OFF position by the Parking Lock
Solenoid N486 (see page 37). In normal vehicle operation
– P engaged or P not engaged (P hydraulically disengaged)
– the intermediate position is not allowed and is registered as
a DTC after a defined period.
643_077

G747 has the following functions:
›› Monitoring correct operation of the parking lock.

The position of the parking lock is monitored by Transmission
Control Module 2 J1006 with the aid of Parking Lock Sensor
G747 and then communicated to Gearbox Control Unit
1 J743. G747 is part of the interface module of the parking
lock module.

68

›› Providing clearance to start in P (the sensor signal is converted directly to the P/N signal by the Gearbox Control
Unit 1).
›› Generating the indications on the instrument cluster when
the parking lock is not engaged (for example, risk of rolling
and prompting engagement of parking lock/parking
brake).

Temperature sensors
Clutch Temperature Sensor 1 G658
Clutch Temperature Sensor 2 G659
The sensors G658/G659 detect the temperature of the
cooling oil thrown out from the dual clutch by centrifugal
force (centrifugal oil temperature). From that, the clutch
temperature can be deduced and the cooling oil volume
controlled according to demand. In addition, warning messages and diagnostics entries are generated from the centrifugal oil temperature. Refer to page 26.

G490

G487

The sensors G658/G659 are 2 identical combination sensors
each of which also houses a speed sensor and a temperature
sensor within the same housing.
Sensor G658 detects the centrifugal oil temperature of clutch
K1. In the case of G658, the speed sensor G182 is also used
for detecting the transmission input speed1). G658 is connected to the electronic module of the Mechatronic module.
Gearbox Control Unit 1 J743 processes the sensor reading and
operates Clutch Cooling Valve 1 N447 accordingly.

G489

G488

Sensor magnet

643_100

Sensor G659 detects the centrifugal oil temperature of clutch
K2. G659 is connected to the auxiliary hydraulic module,
which in turn is connected to Transmission Control Module 2
J1006. The sensor reading is analyzed and passed on to
Gearbox Control Unit 1 J743 as a temperature reading. J743
then sends J1006 the control variable for operating Clutch
Cooling Valve 2 N448. See schematic diagram on page 72.
The speed sensor in G659 is not used.

G658/G182

Electrical connector for auxiliary hydraulic module
G659

643_074
69

Transmission Fluid Temperature Sensor G93
Temperature sensors in the control module
High temperatures have a detrimental effect on the useful
life and performance of electronic components.
Because the electronic control module is integrated in the
gearbox (immersed in oil), monitoring of the module temperature and, therefore, of the gearbox oil temperature is
very important.
G93 is located on the circuit board of Gearbox Control
Unit 1 J743. Gearbox Control Unit 1 is mounted on an aluminium plate that serves as a heat sink for the electronic
module. Pressure sensors G545 and G546 are also located on
this heat sink. The aluminium plate is directly attached to the
electro-hydraulic control module and is in contact with a
constant flow of cooling oil through an oil channel. Therefore,
the temperature of the aluminium plate closely approximates
to the gearbox oil temperature.

The gearbox oil temperature and the temperature of the
gearbox electronic module are important items of information for the following applications:
››
››
››
››

Temperature monitoring for initiating safety functions
Criterion for various adaptations
Adaptation of gear-shift pressure
Criterion for the warm-up program

Due to demanding requirements regarding component protection, there is another temperature sensor for monitoring
the electronic module temperature which is integrated in the
middle of the electronic components and detects the temperature directly at the electronic components. That sensor
does not have a diagnostics designation of its own.
The readings of the two temperature sensors are constantly
checked against one another for plausibility. If there is a fault
on one of the two temperature sensors, a substitute reading
is generated from the readings of the intact sensor and a
substitute program activated. See temperature monitoring/
safety functions.

G546

G545

J743

G93
Aluminium plate

Electronic module

Electro-hydraulic control module
643_071

Temperature monitoring/safety functions
When temperatures at G93 of approximately 288 °F (139 °C)
are detected, Gearbox Control Unit 1 J743 instigates an
engine torque reduction.
A warning message (“Gearbox too hot. Please adjust driving
style”) is also displayed in the instrument cluster. At DTC is
registered in the fault memory.
70

Cooling oil channel for Gearbox Control Unit 1
J743
643_101

The engine torque is reduced so that it is about 70 Nm when
the oil temperature is approximately 293 °F (145 °C). This
improves the cooling capacity and prevents overheating.

Pressure sensors
Hydraulic Pressure Sensor 1 G545
Hydraulic Pressure Sensor 2 G546
G545 detects the clutch pressure of clutch K1 (actual clutch
pressure).
G546 detects the clutch pressure of clutch K2 (actual clutch
pressure).
The sensors G545 and G546 are used to monitor the clutch
pressure of the respective clutch in each case and for calibrating clutch pressure control and the primary pressure.

The actual clutch pressure is constantly compared with the
specified clutch pressure calculated by Gearbox Control Unit
1 J743 and checked for plausibility. In the event of discrepancies (malfunctions), safety deactivation of the gear train
subset concerned is initiated and the relevant safe mode
program activated.
The two sensors are part of the electronic module, which in
turn forms a single unit with the Mechatronic module – which
again can only be replaced as a complete unit if required.

Other information
You can find information on the following topics in the
Owner's Manual for the vehicle:
›› Transmission faults, fault indications and messages.
›› Tow-starting/towing.

71

Function diagram
The control modules are listed on the vehicle diagnostic
tester under the following Address Words:

To make the descriptions easier to follow, the following
designations are used for the two transmission control
modules:

›› J743 – Dual-Clutch Transmission Mechatronic.
›› 02

››

Gearbox Control Unit 1 J743.

››

Transmission Control Module 2 J1006.

›› J1006 – Transmission Control Module 2.
›› C2
›› J587 – Selector Lever Sensor System Control Module.
›› 81

Wiring colors and symbols:
Ground cable
Positive cable
Transmitted signal
Received signal
Inside the 0BZ transmission
Twisted wires

Selector mechanism

Powertrain CAN

72

Mechatronic module

Key:
E313 Selector Lever

J1006 Transmission Control Module 2 J1006

E681 Parking Lock Indicator Lamp

K320 Parking Lock Indicator Lamp

E816 Parking Lock Button

N110 Parking Lock Indicator Lamp

G93

N433 Sub-Transmission 1 Valve 1
– Gear-shift actuator valve 1 for gear-shift actuator A/gears 5/1

Transmission Fluid Temperature Sensor

G182 Transmission Input Speed Sensor
G488 Gear Position Distance Sensor 2/gear-shift actuator B

N434 Sub-Transmission 1 Valve 2
– Gear-shift actuator valve 3 for gear-shift actuator C/gears 3/7

G489 Gear Position Distance Sensor 3/gear-shift actuator C

N435 Sub-Transmission 1 Valve 3 – clutch valve K1

G490 Gear Position Distance Sensor 4/gear-shift actuator D

N436 Sub-Transmission 1 Valve 4
– gear train subset 1 safety valve

G487 Gear Position Distance Sensor 1/gear-shift actuator A

G545 Hydraulic Pressure Sensor 1

N437 Sub-Transmission 2 Valve 1
– Gear-shift actuator valve 2 for gear-shift actuator B/gears 2/6

G546 Hydraulic Pressure Sensor 2
G612 Transmission Input Speed Sensor 2

N438 Sub-Transmission 2 Valve 2
– Gear-shift actuator valve 4 for gear-shift actuator D/gears R/4

G632 Transmission Input Speed Sensor 1
G658 Clutch Temperature Sensor 1

N439 Sub-Transmission 2 Valve 3
– clutch valve K2

G659 Clutch Temperature Sensor 2
G727 Selector Lever Position Sensor
G747 Parking Lock Sensor

N440 Sub-Transmission 2 Valve 4
– gear train subset 2 safety valve

G868 Transverse Selector Lever Lock Sensor

N447 Clutch Cooling Valve 1 – clutch K1

J587 Selector Lever Sensor System Control Module

N448 Clutch Cooling Valve 2 – clutch K2

J743 Dual-Clutch Transmission Mechatronic

N472 Main Pressure Valve
N486 Parking Lock Solenoid
– holding solenoid for parking lock OFF
N573 Parking Lock Solenoid Valve
– Parking lock engagement valve/PEV
N574 Parking Lock Solenoid Valve 2
– Parking lock disengagement valve/PAV
V577 Transverse Selector Lever Lock Motor
Y5
Parking lock module

Steering wheel
tiptronic controls

Auxiliary hydraulic module

Selector Lever Transmission Range Display

Electrical connectors on Transmission Control Module 2 J1006
Connector A pins 1-80 (T81a on ELSA wiring diagram)
Connector B pins 81-121 (T40a on ELSA wiring diagram)

643_090

73

Hydraulic circuit diagram

Key:
AW

Input shaft

BP

Bypass valve

CPU

Central processing unit
– Outlet point on cooling channel for
control unit

DBV

Pressure limiting valve

DF

Pressure filter

DROP Lubrication point
GS

Gear-shift actuator

GSV

Gear-shift actuator value

HD

Primary pressure valve

HP

Hydraulic pump

K

Clutch

KK

Clutch cooling

KUV

Cooling oil valve

KV

Clutch valve

NH

Normally high1)

NL

Normally low1)

PAV

Parking lock disengagement valve

PEV

Parking lock engagement valve

Parking lock module

PHM Parking lock holding solenoid
RD

Residual pressure valve

SF

Intake filter

SHV

Self-holding valve

SV

Safety valve

TR

Temperature regulator (thermostat)

TW

Output shaft

VOL

Volumetric flow valve

WTK Heat exchanger
– fluid: coolant
WTL

Heat exchanger
– fluid: air

WV

Change-over valve
Auxiliary hydraulic module

1)

Explanation of NL and NH
NL characteristic

P

I

74

NL – Normally low means that the solenoid
valve has a positive current/pressure characteristic. That, in turn, means that as the
control current I increases, so does the
control pressure P.

NH characteristic
P

I

NH – Normally high means that the solenoid valve has a negative characteristic.
That, in turn, means that as the control
current I increases, the control pressure P
decreases.

Valve de-energized = no control pressure (0
mA = 0 bar)

Valve de-energized = maximum control
pressure

If one of these valves fails, the corresponding
hydraulic valve or actuator is not operated
and the associated functions fail.

If one of these valves fails, the corresponding hydraulic valve or actuator is set to its
maximum level, for example, maximum
cooling oil flow rate or primary pressure.

Mechatronic module

643_091a

Key:
N433 Sub-Transmission 1 Valve 1
– Gear-shift actuator valve 1 for gear-shift actuator A/gears 5/1

N440 Sub-Transmission 2 Valve 4
– gear train subset 2 safety valve

N434 Sub-Transmission 1 Valve 2
– Gear-shift actuator valve 3 for gear-shift actuator C/gears 3/7

N447 Clutch Cooling Valve 1
– clutch K1

N435 Sub-Transmission 1 Valve 3
– clutch valve K1

N448 Clutch Cooling Valve 2
– clutch K2

N436 Sub-Transmission 1 Valve 4
– gear train subset 1 safety valve

N472 Main Pressure Valve

N437 Sub-Transmission 2 Valve 1
– Gear-shift actuator valve 2 for gear-shift actuator B/gears 2/6
N438 Sub-Transmission 2 Valve 2
– Gear-shift actuator valve 4 for gear-shift actuator D/gears R/4
N439 Sub-Transmission 2 Valve 3
– clutch valve K2

N486 Parking Lock Solenoid
– holding solenoid for parking lock OFF
N573 Parking Lock Solenoid Valve
– Parking lock engagement valve/PEV
N574 Parking Lock Solenoid Valve 2
– Parking lock disengagement valve/PAV

75

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 “950173 - The OBZ 7-speed Dual Clutch S tronic
Transmission in the 2017 R8”
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.

76

950173
All rights reserved.
Technical specifications subject to
change without notice.
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