ForTwo L3-1.0L (2009)
b4
Right front pressure sensor
b5
Left rear pressure sensor
b6
Right rear pressure sensor
m1
High pressure and return pump
y6
Left front solenoid valve (pressure hold)
y7
Left front solenoid valve (release)
y8
Right front solenoid valve (pressure hold)
y9
Right front solenoid valve (pressure release)
y10
Left rear axle solenoid valve (pressure hold)
y11
Left rear axle solenoid valve (pressure release)
y12
Right rear solenoid valve (pressure hold)
y13
Right rear solenoid valve (pressure release)
y18
Front axle switchover solenoid valve
y19
Rear axle switchover solenoid valve
y22
Front axle inlet solenoid valve
y23
Rear axle inlet solenoid valve
A
Traction system hydraulic unit
B
Master brake cylinder
HZ1
Pump pressure circuit 1 (front axle)
HZ2
Pump pressure circuit 2 (rear axle)
Functional principle
The switching components for ABS, ASR, ESP and EBV are combined in the hydraulic unit.
For control purposes, one 2/2 way valve is used on each wheel for the pressure buildup, pressure hold and pressure release functions.
The high-pressure and return pumps in the hydraulic unit are required for pressure buildup and pressure release during ASR and ESP interventions and
for return delivery during ABS intervention. A damper is fitted to each brake circuit to damp the delivery noise. The low pressure reservoir takes up the
brake fluid during the ABS/ASR or ESP depressurization phase and delivers it to the high pressure/return flow pump.
During ABS, ASR and ESP interventions, the switchover solenoid valves shut off the self-priming pump pressure circuit 1 (front axle) and self-priming
pump pressure circuit 2 (rear axle) between the wheel brakes and the master brake cylinder.
The brake fluid passing through the switchover solenoid valves is directed back to the master brake cylinder.
Pressure limiting
Switchover valves without pressure limiting valves are used on the ESP version installed. Protection against excess pressure is provided by reducing the
maximum permissible current in the coils of the switchover valves (USV) to 1.24 A.
