Subaru Legacy/Outback

1999-2003 of release

Repair and operation of the car

System of dynamic stabilization (VDC) - the general information, the principle of functioning

Scheme of an arrangement of the VDC components and adjacent systems


1 — Gidromodulyator VDC 2 — pressure Valve limiter 3 — the Module of engine management (ECM) 4 — the Main Brake Cylinder (MBC) 5 — the Diagnostic socket 6 — the Control lamp of ABS 7 — the Control lamp of VDC 8 — the Alarm indicator of activation of VDC 9 — the Alarm indicator of shutdown of VDC 10 — the Sensor of an angle of rotation of a steering wheel	11 — the DLC Socket for connection of SSM 12 — Wheel ABS sensors 13 — Rotors of wheel sensors 14 — Wheel cylinders 15 — the Sensor of cross overloads (G) and intensity of withdrawal 16 — TCM 17 — the Module of management of VDC 18 — pressure Sensor 19 — the Switch of deactivation of VDC

The principle of functioning of VDC at drift on turn


1 — braking reaction Forces	2 — the Taking-away moment

The principle of functioning of VDC at insufficient reaction of the car to turn of a wheel


1 — braking reaction Forces	2 — the Taking-away moment

Functioning of the VDC hydromodulator in the mode of normal braking (on the example of a contour of one wheel)


1 — the GTTs Tank 2 — GTTS 3 — pressure Sensor 4 — the Port is open 5 — the Port is closed 6 — the Soaking-up electromagnetic valve 7 — the Gate-type electromagnetic valve 8 — the Control valve 9 — It is deactivated 10 — It is deactivated 11 — the Damping chamber 12 — the Port is open	13 — the Inlet electromagnetic valve 14 — the Pump 15 — the Control valve 16 — It is deactivated 17 — the Electric motor 18 — the Wheel cylinder 19 — the Final electromagnetic valve 20 — the Port is closed 21 — It is deactivated 22 — the Tank

Functioning of the VDC hydromodulator in the mode of dumping of pressure at the squeezed-out pedal of a foot brake (on the example of a contour of one wheel)


1 — the GTTs Tank 2 — GTTS 3 — pressure Sensor 4 — the Port is open 5 — the Port is closed 6 — the Soaking-up electromagnetic valve 7 — the Gate-type electromagnetic valve 8 — the Control valve 9 — It is deactivated 10 — It is deactivated 11 — the Damping chamber	12 — the Port is closed 13 — the Inlet electromagnetic valve 14 — the Pump 15 — the Control valve 16 — It is activated 17 — the Electric motor 18 — the Wheel cylinder 19 — the Final electromagnetic valve 20 — the Port is open 21 — It is activated 22 — the Tank

Functioning of the VDC hydromodulator in the mode of deduction of pressure at the squeezed-out pedal of a foot brake (on the example of a contour of one wheel)


1 — the GTTs Tank 2 — GTTS 3 — pressure Sensor 4 — the Port is open 5 — the Port is closed 6 — the Soaking-up electromagnetic valve 7 — the Gate-type electromagnetic valve 8 — the Control valve 9 — It is deactivated 10 — It is deactivated 11 — the Damping chamber	12 — the Port is closed 13 — the Inlet electromagnetic valve 14 — the Pump 15 — the Control valve 16 — It is activated 17 — the Electric motor 18 — the Wheel cylinder 19 — the Final electromagnetic valve 20 — the Port is closed 21 — It is deactivated 22 — the Tank

Functioning of the VDC hydromodulator in the mode of increase of pressure at the squeezed-out pedal of a foot brake (on the example of a contour of one wheel)


1 — the GTTs Tank 2 — GTTS 3 — pressure Sensor 4 — the Port is open 5 — the Port is closed 6 — the Soaking-up electromagnetic valve 7 — the Gate-type electromagnetic valve 8 — the Control valve 9 — It is deactivated 10 — It is deactivated 11 — the Damping chamber	12 — the Port is open 13 — the Inlet electromagnetic valve 14 — the Pump 15 — the Control valve 16 — It is deactivated 17 — the Electric motor 18 — the Wheel cylinder 19 — the Final electromagnetic valve 20 — the Port is closed 21 — It is deactivated 22 — the Tank

Functioning of the VDC hydromodulator in the mode of increase of pressure at the released pedal of a foot brake (on the example of a contour of one wheel)


1 — the GTTs Tank 2 — GTTS 3 — pressure Sensor 4 — the Port is closed 5 — the Port is open 6 — the Soaking-up electromagnetic valve 7 — the Gate-type electromagnetic valve 8 — the Control valve 9 — It is activated 10 — It is activated 11 — the Damping chamber	12 — the Port is open 13 — the Inlet electromagnetic valve 14 — the Pump 15 — the Control valve 16 — It is deactivated 17 — the Electric motor 18 — the Wheel cylinder 19 — the Final electromagnetic valve 20 — the Port is closed 21 — It is deactivated 22 — the Tank

Functioning of the VDC hydromodulator in the mode of deduction of pressure at the released pedal of a foot brake (on the example of a contour of one wheel)


1 — the GTTs Tank 2 — GTTS 3 — pressure Sensor 4 — the Port is closed 5 — the Port is open 6 — the Soaking-up electromagnetic valve 7 — the Gate-type electromagnetic valve 8 — the Control valve 9 — It is activated 10 — the Reducing valve 11 — It is activated 12 — the Damping chamber	13 — the Port is closed 14 — the Inlet electromagnetic valve 15 — the Pump 16 — the Control valve 17 — It is activated 18 — the Electric motor 19 — the Wheel cylinder 20 — the Final electromagnetic valve 21 — the Port is closed 22 — It is deactivated 23 — the Tank

Functioning of the VDC hydromodulator in the mode of dumping of pressure at the released pedal of a foot brake (on the example of a contour of one wheel)


1 — the GTTs Tank 2 — GTTS 3 — pressure Sensor 4 — the Port is closed 5 — the Port is open 6 — the Soaking-up electromagnetic valve 7 — the Gate-type electromagnetic valve 8 — the Control valve 9 — It is activated 10 — the Reducing valve 11 — It is activated 12 — the Damping chamber	13 — the Port is closed 14 — the Inlet electromagnetic valve 15 — the Pump 16 — the Control valve 17 — It is activated 18 — the Electric motor 19 — the Wheel cylinder 20 — the Final electromagnetic valve 21 — the Port is open 22 — It is activated 23 — the Tank

The VDC system represents system with the return the communication allowing to keep course stability at the movement of the vehicle in various modes (full or partial braking, the movement by a setup, dispersal, braking by the engine, change of loadings, performance of extreme maneuvers and so forth) VDC is combined with ABS and antiprobuksovochny system / monitoring system of draft (TCS), logically developing the advantages provided by them.

The scheme of placement of the VDC components and adjacent systems is submitted on an illustration.

The VDC system anticipates "advancing" or "delay" of an entrance of the car to turn at the movement on roads with a slippery covering. The module of management of VDC reveals intentions of the driver on commission of maneuvers on the basis of the analysis of information arriving from sensors of an angle of rotation of a steering wheel, brake pressure, tracking of working parameters of the power unit and so forth. At the same time, being guided by indications of ABS sensors, cross overloads (G), the taking-away moment and so forth, the system estimates reaction of the car to actions of the driver. Comparing the arriving information to the basic parameters put in memory of the processor, the module of management reveals tendencies to the drifts connected with insufficiency or excessiveness of sensitivity of the vehicle and in due time provides creation of the counteracting efforts due to individual activation of brake mechanisms, corrections of traction effort of the engine and management of connection of the full drive (through TCM of automatic transmission), i.e., activating the corresponding ABS and TCS functions.

Principle of functioning of VDC

Suppression of "excessive" reaction of the car turn of a wheel ("advancing")

At the time of the beginning of withdrawal (drift) of back part of the car as a result of excessive reaction to turn of a wheel the module of management of VDC activates wheel cylinders of brake mechanisms of both external wheels that leads to emergence of force counteracting the taking-away moment.

Suppression of "insufficient" reaction of the car to turn of a wheel ("delay")

If at a car entrance to turn the front starts taking away (to take down) in the course direction, the module of management of VDC activates brake mechanisms of both "internal" wheels, creating the reaction force compensating the taking-away moment connected with demolition of a front.

Module of management of VDC

On the basis of the data arriving from the corresponding information sensors, the module exercises control of functioning of the VDC hydromodulator, and also makes activation of separate ABS devices and antiprobuksovochny system / monitoring system of draft (TCS).

Data exchange of the module of management of VDC with TCM of automatic transmission and the sensor of turn of a steering wheel is carried out on the tire CAN.

In case of identification of violations of serviceability of functioning the VDC module of management provides shutdown of system and activation of the corresponding control lamp on an instrument guard of the car. Codes of the revealed refusals remain in memory of the processor.

VDC hydromodulator

The hydromodulator at the command of the module of management provides activation of pump assembly and switching of the electromagnetic valves controlling supply of brake fluid to wheel cylinders.

Principle of functioning of the hydromodulator

The mode of normal braking (ABS is not activated)

In the mode of normal braking any of electromagnetic valves is not activated (ports of inlet and gate-type valves are open, final and soaking up - are closed). The pressure of hydraulic liquid developed in GTTs completely is transferred to the wheel cylinder through open ports of gate-type and inlet valves.

The mode of dumping of pressure at the squeezed-out pedal of a foot brake

Inlet and final electromagnetic valves are activated, all other - no. Thus, ports of the inlet and soaking-up valves are closed, final and gate-type - are open. In spite of the fact that the pressure of GTTs is transmitted through open port of the soaking-up valve, further distribution pressure is blocked by the closed inlet valve, on the other hand, so far the port of the final valve is open, brake fluid freely flows from the wheel cylinder in the tank that leads to dumping of hydraulic pressure and weakening of brake effort.

From the tank brake fluid is pumped over by the pump back in GTTs.

The mode of deduction of pressure at the squeezed-out pedal of a foot brake

In this mode only the inlet electromagnetic valve is activated, i.e. ports of all valves except the gate-type are closed. The liquid pressure from GTTs through open port of the gate-type valve moves on the inlet valve, but does not pass further. As the port of the final valve is also closed, pressure continues to keep in the wheel cylinder.

During all cycle of this mode the pump continues to work on commands of the module of management of VDC.

The mode of increase of pressure at the squeezed-out pedal of a foot brake

All electromagnetic valves are deactivated, as well as in the mode of normal braking. The pressure of hydraulic liquid from GTTs through open ports of gate-type and inlet valves is transferred to the wheel cylinder, providing increase of pressure.

The pump continues to work on commands of the module of management of VDC during all cycle.

The mode of increase of pressure at the released pedal of a foot brake

In this mode only the gate-type and soaking-up valves are activated, inlet and final remain deactivated. Thus, ports of gate-type and final valves are closed, inlet and gate-type - are open and the pump provides pumping of brake fluid from the GTTs tank in the wheel cylinder through open ports of the soaking-up and inlet valves that leads to activation of the brake mechanism.

The mode of deduction of pressure at the released pedal of a foot brake

All electromagnetic valves, except the final are activated. Thus, ports of all valves, except the soaking up are closed. the pump provides pumping of brake fluid of the GTTs tank through open port of the soaking-up valve, however further the section of a path through passage is blocked by the closed port of the inlet valve. The closed port of the final valve prevents dumping of pressure in the wheel cylinder, moreover, due to functioning of the pump it continues to grow as the port of the inlet valve remains closed. At achievement the opening of the reducing assembly which is built in assembly of the gate-type valve providing return of excess of liquid back in the GTTs tank happens pressure of some certain size.

The mode of dumping of pressure at the released pedal of a foot brake

All electromagnetic valves are activated, i.e., ports of the gate-type and inlet valve are closed, soaking up and final - are open. Thus the pump provides an intake of brake fluid from the tank and its giving to GTTs through open port of the soaking-up valve. As the inlet valve is closed, liquid does not get to the wheel cylinder while its outflow from the cylinder in the tank is provided through open port of the final valve. As a result pressure in the wheel cylinder is dumped. From the tank brake fluid is pumped over to GTTs via the open soaking-up valve. Thus the pressure of the liquid given by the pump on the closed gate-type valve continues to grow and on reaching limit admissible value is dumped through reducing assembly in the GTTs tank.

Sensor of turn of a steering wheel

The sensor issues information on the direction and size of an angle of rotation of a steering wheel on the module of management.

The sensor of cross overloads (G) and the taking-away moment

On the basis of information arriving from the sensor the module of management of VDC estimates reaction of the car to actions of the driver when performing maneuvers.

Wheel ABS sensors

ABS sensors carry out the regular function on control of frequency of rotation of turns of each of car wheels.

Module of engine management (ECM)

ECM exercises control of output parameters of the engine according to the data arriving from the module of management of VDC and also delivers on the last information on the current working parameters and turns of the power unit.

Module of management of AT (TCM)

TCM exercises control of couplings of coupling of AT, correcting traction effort according to the data arriving from the module of management of VDC.

Control lamp of ABS

The control lamp serves for the warning of the driver of refusals of system of anti-blocking of brakes (ABS).

Control lamp of VDC

This control lamp warns the driver about malfunctions in systems of dynamic stabilization (VDC) and TCS.

Alarm indicator of activation of VDC

Being activated in flashing (VDC) or the constant (TCS) mode, the indicator warns the driver about operation of the relevant system.

Alarm indicator of shutdown of VDC (VDC OFF)

The indicator is activated at compulsory shutdown of VDC/TCS systems at the command of the user.

Switch of deactivation of VDC

The switch is located on console section of the dashboard under assembly with the radio receiver and allows the driver to make temporary compulsory shutdown of system of dynamic stabilization.

Shutdown of VDC is possible only at speeds of the movement of the car lower than 60 km/h (38 miles/h).

Keeping of the button of the VDC switch pressed within more than 10 seconds leads to shutdown of the alarm indicator "VDC OFF" then the button is blocked and use of it becomes possible only after restart of the engine.

Automatic activation of the disconnected VDC system happens at increase of speed of the movement of the car to 60 km/h (38 miles/h).

Need for shutdown of VDC when a certain probuksovyvaniye of wheels is useful, can arise in the following cases:

a) At a start of motion on the ice-covered or going abruptly uphill road;
b) In attempts to get out of dirt or a snowdrift in case of a uvyazaniye of all four wheels.