Component Description
| Component | Reference/Function | |
|---|---|---|
| 1 | Steering angle sensor | " STEERING ANGLE SENSOR " |
| 2 | VDC OFF switch | " VDC OFF SWITCH " |
| 3 | IPDM E/R | " COMPONENT PARTS LOCATION " |
| 4 | Brake fluid level switch | " BRAKE FLUID LEVEL SWITCH " |
| 5 | ABS actuator and electric unit (control unit) | " ABS ACTUATOR AND ELECTRIC UNIT (CONTROL UNIT) " |
| 6 | Front wheel sensor | " WHEEL SENSOR AND SENSOR ROTOR " |
| 7 | Stop lamp switch | " STOP LAMP SWITCH " |
| 8 | Parking brake switch | " PARKING BRAKE SWITCH " |
| 9 | Rear wheel sensor | " WHEEL SENSOR AND SENSOR ROTOR " |
| 10 | Combination meter | " METER SYSTEM: COMBINATION METER " |
VDC/TCS/ABS: System Description
- The system switches fluid pressure of each brake caliper and each wheel cylinder to increase, to hold, or to decrease according to signals from control unit in ABS actuator and electric unit (control unit). This control system is applied to VDC, TCS, ABS and EBD functions.
- Fail-safe function is available for each function and is activated by each function when system malfunction occurs.
VALVE OPERATION (VDC AND TCS FUNCTIONS)
The control unit built in the ABS actuator and electric unit (control unit) controls fluid pressure of the brake calipers by operating each valve.
VDC and TCS Functions are Operating (Pressure Increases)
Scheme 1
| Name | Not activated | Pressure increases |
|---|---|---|
| Cut valve 1 | Power supply is not supplied (open) | Power supply is supplied (close) |
| Cut valve 2 | Power supply is not supplied (open) | Power supply is supplied (close) |
| Suction valve 1 | Power supply is not supplied (close) | Power supply is supplied (open) |
| Suction valve 2 | Power supply is not supplied (close) | Power supply is supplied (open) |
| ABS IN valve | Power supply is not supplied (open) | Power supply is not supplied (open) |
| ABS OUT valve | Power supply is not supplied (close) | Power supply is not supplied (close) |
| Each brake caliper and each wheel cylinder (fluid pressure) | Pressure increases |
Front RH brake caliper
- Brake fluid is conveyed to the pump from the master cylinder through suction valve 1 and is pressurized by the pump operation. The pressurized brake fluid is supplied to the front RH brake caliper through the ABS IN valve. For the left caliper, brake fluid pressure is maintained because the pressurization is unnecessary. The pressurization for the left caliper is controlled separately from the right caliper.
Front LH brake caliper
- Brake fluid is conveyed to the pump from the master cylinder through suction valve 2 and is pressurized by the pump operation. The pressurized brake fluid is supplied to the front LH brake caliper through the ABS IN valve. For the right caliper, brake fluid pressure is maintained because the pressurization is unnecessary. The pressurization for the right caliper is controlled separately from the left caliper.
Rear RH wheel cylinder
- Brake fluid is conveyed to the pump from the master cylinder through suction valve 2 and is pressurized by the pump operation. The pressurized brake fluid is supplied to the rear RH wheel cylinder through the ABS IN valve. For the left wheel cylinder, brake fluid pressure is maintained because the pressurization is unnecessary. The pressurization for the left wheel cylinder is controlled separately from the right wheel cylinder.
Rear LH wheel cylinder
- Brake fluid is conveyed to the pump from the master cylinder through suction valve 1 and is pressurized by the pump operation. The pressurized brake fluid is supplied to the rear LH wheel cylinder through the ABS IN valve. For the right wheel cylinder, brake fluid pressure is maintained because the pressurization is unnecessary. The pressurization for the right wheel cylinder is controlled separately from the left wheel cylinder.
VDC and TCS Functions Start Operating (Pressure Holds)
Scheme 2
| Name | Not activated | Pressure holds |
|---|---|---|
| Cut valve 1 | Power supply is not supplied (open) | Power supply is supplied (close) |
| Cut valve 2 | Power supply is not supplied (open) | Power supply is supplied (close) |
| Suction valve 1 | Power supply is not supplied (close) | Power supply is not supplied (close) |
| Suction valve 2 | Power supply is not supplied (close) | Power supply is not supplied (close) |
| ABS IN valve | Power supply is not supplied (open) | Power supply is not supplied (open) |
| ABS OUT valve | Power supply is not supplied (close) | Power supply is not supplied (close) |
| Each brake caliper and wheel cylinder (fluid pressure) | Pressure holds |
Front RH brake caliper
- Since the cut valve 1 and the suction valve 1 are closed, the front RH brake caliper, master cylinder, and reservoir are blocked. This maintains fluid pressure applied on the front RH brake caliper. The pressurization for the left caliper is controlled separately from the right caliper.
Front LH brake caliper
- Since the cut valve 2 and the suction valve 2 are closed, the front LH brake caliper, master cylinder, and reservoir are blocked. This maintains fluid pressure applied on the front LH brake caliper. The pressurization for the right caliper is controlled separately from the left caliper.
Rear RH wheel cylinder
- Since the cut valve 2 and the suction valve 2 are closed, the rear RH wheel cylinder, master cylinder, and reservoir are blocked. This maintains fluid pressure applied on the rear RH wheel cylinder. The pressurization for the left wheel cylinder is controlled separately from the right wheel cylinder.
Rear LH wheel cylinder
- Since the cut valve 1 and the suction valve 1 are closed, the rear LH wheel cylinder, master cylinder, and reservoir are blocked. This maintains fluid pressure applied on the rear LH wheel cylinder. The pressurization for the right wheel cylinder is controlled separately from the left wheel cylinder.
VDC and TCS Functions Operating (Pressure Decreases)
Scheme 3
| Name | Not activated | During pressure decreases |
|---|---|---|
| Cut valve 1 | Power supply is not supplied (open) | Power supply is not supplied (open) |
| Cut valve 2 | Power supply is not supplied (open) | Power supply is not supplied (open) |
| Suction valve 1 | Power supply is not supplied (close) | Power supply is not supplied (close) |
| Suction valve 2 | Power supply is not supplied (close) | Power supply is not supplied (close) |
| ABS IN valve | Power supply is not supplied (open) | Power supply is not supplied (open) |
| ABS OUT valve | Power supply is not supplied (close) | Power supply is not supplied (close) |
| Each brake caliper and each wheel cylinder (fluid pressure) | Pressure decreases |
Front RH brake caliper
- Since the suction valve 1 and the ABS OUT valve are closed and the cut valve 1 and the ABS IN valve are open, the fluid pressure applied on the front RH brake caliper is reduced by supplying the fluid pressure to the master cylinder via the ABS IN valve and the cut valve 1. The pressurization for the right caliper is controlled separately from the left caliper.
Front LH brake caliper
- Since the suction valve 2 and the ABS OUT valve are closed and the cut valve 2 and the ABS IN valve are open, the fluid pressure applied on the front LH brake caliper is reduced by supplying the fluid pressure to the master cylinder via the ABS IN valve and the cut valve 2. The pressurization for the left caliper is controlled separately from the right caliper.
Rear RH wheel cylinder
- Since the suction valve 2 and the ABS OUT valve are closed and the cut valve 2 and the ABS IN valve are open, the fluid pressure applied on the rear RH wheel cylinder is reduced by supplying the fluid pressure to the master cylinder via the ABS IN valve and the cut valve 2. The pressurization for the right wheel cylinder is controlled separately from the left wheel cylinder.
Rear LH wheel cylinder
- Since the suction valve 1 and the ABS OUT valve are closed and the cut valve 1 and the ABS IN valve are open, the fluid pressure applied on the rear LH wheel cylinder is reduced by supplying the fluid pressure to the master cylinder via the ABS IN valve and the cut valve 1. The pressurization for the left wheel cylinder is controlled separately from the right wheel cylinder.
| Component | Function |
|---|---|
| Pump | Returns the brake fluid reserved in reservoir to master cylinder by reducing pressure. |
| Motor | Activates the pump according to signals from ABS actuator and electric unit (control unit). |
| Cut valve 1 Cut valve 2 | Shuts off the ordinary brake line from master cylinder. |
| Suction valve 1 Suction valve 2 | Supplies the brake fluid from master cylinder to the pump. |
| ABS IN valve | Switches the fluid pressure line to increase or hold according to signals from control unit. |
| ABS OUT valve | Switches the fluid pressure line to increase, hold or decrease according to signals from control unit. |
| Return check valve | Returns the brake fluid from brake caliper and wheel cylinder to master cylinder by bypassing orifice of each valve when brake is released. |
| Reservoir | Temporarily reserves the brake fluid drained from brake caliper, so that pressure efficiently decreases when decreasing pressure of brake caliper and wheel cylinder. |
| Pressure sensor | Detects the brake fluid pressure and transmits signal to ABS actuator and electric unit (control unit). |
COMPONENT PARTS FUNCTION DESCRIPTION
VALVE OPERATION (ABS AND EBD FUNCTIONS)
The control unit built into the ABS actuator and electric unit (control unit) controls fluid pressure of the brake calipers by operating each valve.
Brake Pedal Applied or ABS Function Operating (Pressure Increases)
Scheme 4
| Name | Not activated | During pressure increases |
|---|---|---|
| Cut valve 1 | Power supply is not supplied (open) | Power supply is not supplied (open) |
| Cut valve 2 | Power supply is not supplied (open) | Power supply is not supplied (open) |
| Suction valve 1 | Power supply is not supplied (close) | Power supply is not supplied (close) |
| Suction valve 2 | Power supply is not supplied (close) | Power supply is not supplied (close) |
| ABS IN valve | Power supply is not supplied (open) | Power supply is not supplied (open) |
| ABS OUT valve | Power supply is not supplied (close) | Power supply is not supplied (close) |
| Each brake caliper and each wheel cylinder (fluid pressure) | Pressure increases |
Front RH brake caliper
- When the cut valve 1 and the ABS IN valve opens, brake fluid is supplied to the front RH brake caliper from the master cylinder through the ABS IN valve. Brake fluid does not flow into the reservoir because the ABS OUT valve is closed.
Front LH brake caliper
- When the cut valve 2 and the ABS IN valve opens, brake fluid is supplied to the front LH brake caliper from the master cylinder through the ABS IN valve. Brake fluid does not flow into the reservoir because the ABS OUT valve is closed.
Rear RH wheel cylinder
- When the cut valve 2 and the ABS IN valve opens, brake fluid is supplied to the rear RH wheel cylinder from the master cylinder through the ABS IN valve. Brake fluid does not flow into the reservoir because the ABS OUT valve is closed.
Rear LH wheel cylinder
- When the cut valve 1 and the ABS IN valve opens, brake fluid is supplied to the rear LH wheel cylinder from the master cylinder through the ABS IN valve. Brake fluid does not flow into the reservoir because the ABS OUT valve is closed.
ABS Function Starts Operating (Pressure Holds)
Scheme 5
| Name | Not activated | During pressure holds |
|---|---|---|
| Cut valve 1 | Power supply is not supplied (open) | Power supply is not supplied (open) |
| Cut valve 2 | Power supply is not supplied (open) | Power supply is not supplied (open) |
| Suction valve 1 | Power supply is not supplied (close) | Power supply is not supplied (close) |
| Suction valve 2 | Power supply is not supplied (close) | Power supply is not supplied (close) |
| ABS IN valve | Power supply is not supplied (open) | Power supply is supplied (close) |
| ABS OUT valve | Power supply is not supplied (close) | Power supply is not supplied (close) |
| Each brake caliper and each wheel cylinder (fluid pressure) | Pressure holds |
Front RH brake caliper
- Since the ABS IN valve and the ABS OUT valve are closed, the front RH brake caliper, master cylinder, and reservoir are blocked. This maintains fluid pressure applied on the front RH brake caliper.
Front LH brake caliper
- Since the ABS IN valve and the ABS OUT valve are closed, the front LH brake caliper, master cylinder, and reservoir are blocked. This maintains fluid pressure applied on the front LH brake caliper.
Rear RH wheel cylinder
- Since the ABS IN valve and the ABS OUT valve are closed, the rear RH wheel cylinder, master cylinder, and reservoir are blocked. This maintains fluid pressure applied on the rear RH wheel cylinder.
Rear LH wheel cylinder
- Since the ABS IN valve and the ABS OUT valve are closed, the rear LH wheel cylinder, master cylinder, and reservoir are blocked. This maintains fluid pressure applied on the rear LH wheel cylinder.
ABS Function Operating (Pressure Decreases)
Scheme 6
| Name | Not activated | During pressure decreases |
|---|---|---|
| Cut valve 1 | Power supply is not supplied (open) | Power supply is not supplied (open) |
| Cut valve 2 | Power supply is not supplied (open) | Power supply is not supplied (open) |
| Suction valve 1 | Power supply is not supplied (close) | Power supply is not supplied (close) |
| Suction valve 2 | Power supply is not supplied (close) | Power supply is not supplied (close) |
| ABS IN valve | Power supply is not supplied (open) | Power supply is supplied (close) |
| ABS OUT valve | Power supply is not supplied (close) | Power supply is supplied (open) |
| Each brake caliper and each wheel cylinder (fluid pressure) | Pressure decreases |
Front RH brake caliper
- Since the ABS IN valve is closed and the ABS OUT valve is opened, fluid pressure applied on the front RH brake caliper is supplied to the reservoir through the ABS OUT valve. This fluid pressure decreases when sent to the master cylinder by the pump.
Front LH brake caliper
- Since the ABS IN valve is closed and the ABS OUT valve is opened, fluid pressure applied on the front LH brake caliper is supplied to the reservoir through the ABS OUT valve. This fluid pressure decreases when sent to the master cylinder by the pump.
Rear RH wheel cylinder
- Since the ABS IN valve is closed and the ABS OUT valve is opened, fluid pressure applied on the rear RH wheel cylinder is supplied to the reservoir through the ABS OUT valve. This fluid pressure decreases when sent to the master cylinder by the pump.
Rear LH wheel cylinder
- Since the ABS IN valve is closed and the ABS OUT valve is opened, fluid pressure applied on the rear LH wheel cylinder is supplied to the reservoir through the ABS OUT valve. This fluid pressure decreases when sent to the master cylinder by the pump.
ABS Function Operating (Pressure Increases)
| Name | Not activated | During pressure increases |
|---|---|---|
| Cut valve 1 | Power supply is not supplied (open) | Power supply is not supplied (open) |
| Cut valve 2 | Power supply is not supplied (open) | Power supply is not supplied (open) |
| Suction valve 1 | Power supply is not supplied (close) | Power supply is not supplied (close) |
| Suction valve 2 | Power supply is not supplied (close) | Power supply is not supplied (close) |
| ABS IN valve | Power supply is not supplied (open) | Power supply is not supplied (open) |
| ABS OUT valve | Power supply is not supplied (close) | Power supply is not supplied (close) |
| Each brake caliper and each wheel cylinder (fluid pressure) | Pressure increases |
Front RH brake caliper
- Brake fluid is supplied to the front RH brake caliper from the master cylinder through the cut valve 1 and the ABS IN valve. Since the suction valve 1 and the ABS OUT valve is closed, the fluid does not flow into the reservoir. The amount of brake fluid supplied to the front RH brake caliper from the master cylinder is controlled according to time that the ABS IN valve is not energized (time that the ABS IN valve is open).
Front LH brake caliper
- Brake fluid is supplied to the front LH brake caliper from the master cylinder through the cut valve 2 and the ABS IN valve. Since the suction valve 2 and the ABS OUT valve is closed, the fluid does not flow into the reservoir. The amount of brake fluid supplied to the front LH brake caliper from the master cylinder is controlled according to time that the ABS IN valve is not energized (time that the ABS IN valve is open).
Rear RH wheel cylinder
- Brake fluid is supplied to the rear RH wheel cylinder from the master cylinder through the cut valve 2 and the ABS IN valve. Since the suction valve 2 and the ABS OUT valve is closed, the fluid does not flow into the reservoir. The amount of brake fluid supplied to the rear RH wheel cylinder from the master cylinder is controlled according to time that the ABS IN valve is not energized (time that the ABS IN valve is open).
Rear LH wheel cylinder
- Brake fluid is supplied to the rear LH wheel cylinder from the master cylinder through the cut valve 1 and the ABS IN valve. Since the suction valve 1 and the ABS OUT valve is closed, the fluid does not flow into the reservoir. The amount of brake fluid supplied to the rear LH wheel cylinder from the master cylinder is controlled according to time that the ABS IN valve is not energized (time that the ABS IN valve is open).
Brake Release
Scheme 7
| Name | Not activated | During brake release |
|---|---|---|
| Cut valve 1 | Power supply is not supplied (open) | Power supply is not supplied (open) |
| Cut valve 2 | Power supply is not supplied (open) | Power supply is not supplied (open) |
| Suction valve 1 | Power supply is not supplied (close) | Power supply is not supplied (close) |
| Suction valve 2 | Power supply is not supplied (close) | Power supply is not supplied (close) |
| ABS IN valve | Power supply is not supplied (open) | Power supply is not supplied (open) |
| ABS OUT valve | Power supply is not supplied (close) | Power supply is not supplied (close) |
| Each brake caliper and each wheel cylinder (fluid pressure) | Pressure decreases |
Front RH brake caliper
- Brake fluid is supplied to the front RH brake caliper through the return check valve of the ABS IN valve and the cut valve 1, and returns to the master cylinder.
Front LH brake caliper
- Brake fluid is supplied to the front LH brake caliper through the return check valve of the ABS IN valve and the cut valve 2, and returns to the master cylinder.
Rear RH wheel cylinder
- Brake fluid is supplied to the rear RH wheel cylinder through the return check valve of the ABS IN valve and the cut valve 2, and returns to the master cylinder.
Rear LH wheel cylinder
- Brake fluid is supplied to the rear LH wheel cylinder through the return check valve of the ABS IN valve and the cut valve 1, and returns to the master cylinder.
Component Parts and Function
| Component | Function |
|---|---|
| Pump | Returns the brake fluid reserved in reservoir to master cylinder by reducing pressure. |
| Motor | Activates the pump according to signals from ABS actuator and electric unit (control unit). |
| Cut valve 1 Cut valve 2 | Shuts off the ordinary brake line from master cylinder. |
| Suction valve 1 Suction valve 2 | Supplies the brake fluid from master cylinder to the pump. |
| ABS IN valve | Switches the fluid pressure line to increase or hold according to signals from control unit. |
| ABS OUT valve | Switches the fluid pressure line to increase, hold or decrease according to signals from control unit. |
| Return check valve | Returns the brake fluid from brake caliper and wheel cylinder to master cylinder by bypassing orifice of each valve when brake is released. |
| Reservoir | Temporarily reserves the brake fluid drained from brake caliper, so that pressure efficiently decreases when decreasing pressure of brake caliper and wheel cylinder. |
| Pressure sensor | Detects the brake fluid pressure and transmits signal to ABS actuator and electric unit (control unit). |
OPERATION CHARACTERISTICS
VDC Function That Prevents Oversteer Tendency
Scheme 8
Scheme 9
- During cornering, brake force (brake fluid pressure) is applied on front wheel and rear wheel on the outer side of turn. Momentum is generated directing the vehicle toward the outer side of the turn. Oversteer is prevented.
- Changing driving lane on a slippery road, when there may be a tendency to oversteer, engine output is controlled as well as brake force (brake fluid pressure) of 4 wheels. Oversteer tendency decreases.
VDC Function That Prevents Understeer Tendency
Scheme 10
Scheme 11
- During cornering, brake force (brake fluid pressure) is applied on front wheel and rear wheel on the inner side of turn. Momentum is generated directing the vehicle toward the inner side of the turn. Understeer is prevented.
- Applying brakes during cornering on a slippery road, when there may be a tendency to understeer, engine output is controlled as well as brake force (brake fluid pressure) of 4 wheels. Understeer tendency decreases.
Scheme 12
- Wheel spin status of drive wheel is detected by wheel sensor of 4 wheels. Engine output and transmission shift status is controlled so that slip rate of drive wheels is in appropriate level. When wheel spin occurs on drive wheel, ABS actuator and electric unit (control unit) perform brake force control of LH and RH drive wheels (apply brake force by increasing brake fluid pressure of drive wheel) and decrease engine torque by engine torque control. Wheel spin amount decreases. Engine torque is controlled to appropriate level.
- TCS function can be switched to non-operational status (OFF) by operating VDC OFF switch. In this case, VDC OFF indicator lamp turns ON.
- SLIP indicator lamp blinks while TCS function is in operation and indicates to the driver that the function is in operation.
- CONSULT can be used to diagnose the system.
- Fail-safe function is adopted. When a malfunction occurs in TCS function, the control is suspended for VDC function and TCS function. However, ABS function and EBD function operate normally. Refer to " «FAIL-SAFE»(ref-675599-S06844757042014120500000) ".
ECU IDENTIFICATION
ABS actuator and electric unit (control unit) part number is displayed.
Operation Procedure
- Before performing the self-diagnosis, start engine and drive vehicle at 30 km/h (19 MPH) or more for approximately 1 minute.
Description
After replacing the ABS actuator and electric unit (control unit), perform the neutral position adjustment for the steering angle sensor. Refer to " WORK PROCEDURE ".
Refer to the table below to determine if adjustment of steering angle sensor neutral position is required.
| X: Required -: Not required | |
|---|---|
| Situation | Adjustment of steering angle sensor neutral position |
| Removing/Installing ABS actuator and electric unit (control unit) | |
| Replacing ABS actuator and electric unit (control unit) | X |
| Removing/Installing steering angle sensor | X |
| Replacing steering angle sensor | X |
| Removing/Installing steering components | X |
| Replacing steering components | X |
| Removing/Installing suspension components | X |
| Replacing suspension components | X |
| Change tires to new ones | |
| Tire rotation | |
| Adjusting wheel alignment | X |
Initial diagnosis of ABS actuator and electric unit (control unit)
| Symptom | Result |
|---|---|
| Slight vibrations are felt on the brake pedal and operation noises occur when VDC, TCS or ABS is activated. | This is a normal condition due to the VDC, TCS or ABS activation. |
| Stopping distance is longer than that of vehicles without ABS when the vehicle drives on rough, gravel, or snow-covered (fresh, deep snow) roads. | |
| The brake pedal moves and generates noises when TCS or VDC is activated due to rapid acceleration or sharp turn. | |
| The brake pedal vibrates and motor operation noises occur from the engine room after the engine starts and just after the vehicle starts. | This is normal, and it is caused by the ABS operation check. |
| Depending on the road conditions, the driver may experience a sluggish feel in the brake pedal. | This is normal, because TCS places the highest priority on the optimum traction (stability). |
| TCS may activate momentarily if wheel speed changes when driving where road friction coefficient varies, when downshifting, or when fully depressing accelerator pedal. | |
| The ABS warning lamp and SLIP indicator lamp may turn ON when the vehicle is subject to strong shaking or large vibration, such as when the vehicle is rotating on a turntable or located on a ship while the engine is running. | In this case, restart the engine on a normal road. If the normal condition is restored, there is no malfunction. At that time, erase the self-diagnosis memory. |
| VDC may not operate normally or the ABS warning lamp, and SLIP indicator lamp may illuminate when driving on a road that is extremely slanted (e.g., bank in a circuit course). | |
| A malfunction may occur in the yaw rate/side/decel G sensor system when the vehicle turns sharply, such as during a spin turn, axle turn, or drift driving, while the VDC function is OFF (VDC OFF indicator lamp illuminated). | |
| The vehicle speed will not increase even though the accelerator pedal is depressed, when inspecting the speedometer on a 2-wheel chassis dynamometer. | Normal (Deactivate the VDC/TCS function before performing an inspection on a chassis dynamometer.) |
| SLIP indicator lamp may simultaneously turn ON when low tire pressure warning lamp turns ON. | This is not a VDC system error but results from characteristic change of tire. |
Scheme 13
See also:
• DIAGNOSIS PROCEDURE
• DIAGNOSIS PROCEDURE