55
M
B
M
A
Md
M
A
M
A
M
A
If faulty signals are generated or if CAN mes-
sages cannot be received, the vehicle switches
to emergency mode.
If speed signals are missing, the coupling is
opened fully for safety reasons.
The Haldex viscous coupling does not have
any sensors of its own apart from a tempera-
ture sensor (necessary for compensating for
temperature-dependent oil viscosity).
The system conditions the signals which the
CAN-BUS supplies (ABS/EDL control unit,
engine control unit).
These are
– speed of each individual wheel
– engine torque
– engine speed
– driving condition (straight-ahead driving,
thrust, braking, ABS)
– accelerator pedal position/throttle valve
The control system can recognise corners,
manoeuvring mode, acceleration phase and
different wheel circumferences. The stiffness
of the Haldex viscous coupling is adjusted
according to the recognised driving conditi-
ons.
The control system
Legend
ABS/EDL sensor line
ABS/EDL control line
Brake line, pressurised
Brake line, depressurised
M
A
Drive torque per wheel
M
B
Brake torque per wheel
M
d
Engine torque
Accelerator pedal position,
Engine torque,
Engine speed
Wheel speeds
Wheel speed front right > front left
Wheel speed rear right > rear left
Low coefficient of friction
Engine control unit
Haldex
control
unit
Haldex
viscous
coupling
ABS/EDL
hydraulic unit
Motive force, front
ABS/EDL control unit
Motive force, rear
High coefficient of friction
SSP207/10
The Haldex viscous coupling is inte-
grated in the vehicle self-diagnosis.
Address word: 22 – 4wd electronics.
