Electronically Controlled Brake System (Ebs) (Diagnostics - Introduction): Other Lexus GS III facelift

PRECAUTION

Note. When disconnecting the cable from the negative (-) battery terminal, initialize the following systems after the cable is reconnected.

1. TROUBLESHOOTING PRECAUTIONS When there is a malfunction with terminal contact points or problem with part installation, removal and installation of the suspected problem parts may return the system to the normal condition either completely or temporarily. In order to determine the malfunctioning area, be sure to check the conditions at the time the malfunction occurred, such as DTC output and the Freeze Frame Data, and record it before disconnecting each connector or removing and installing parts. Since this system may be influenced by malfunctions in systems other than the brake control system, be sure to also check for DTCs in other systems.
2. HANDLING PRECAUTIONS Do not remove or install the Electronically Controlled Brake System parts such as the steering sensor, yaw rate sensor or brake pedal stroke sensor except when required, as they need to be adjusted correctly after removal or installation. Be sure to complete preparation before work and confirmation after work by following the direction in the repair manual when working on the Electronically Controlled Brake System. Be sure to remove and install the ECU, actuator, each sensor, etc. with the engine switch off unless it is not specified in the inspection procedure. Be sure to remove the 2 main relays before removal and installation, or replacement of the Electronically Controlled Brake System parts. The removal or installation of the actuator, master cylinder or stroke simulator as well as some other procedures can cause the fluid level to drop below the fluid reservoir port. If this happens when performing such work, be sure to remove the 2 motor relays before the bleeding of the air in the pipeline is completed. HINT: When the pump motor is operated with the air in the brake actuator hose, bleeding of the air becomes difficult due to the air in the actuator. The skid control ECU may operate the stroke simulator and drive the pump motor even when the engine switch is turned off. Even with the engine switch turned off, the skid control ECU can be operated for 2 minutes after the brake operation is finished. Removal of the main relay and motor relay. With the engine switch OFF and the driver door closed, wait for 2 minutes without depressing the brake pedal. Make sure the brake control system is off. Then remove the 2 relays. HINT: Just before the brake control system turns off, the pump motor will operate for several seconds to prepare for its next operation. When removing and installing the ECU, actuator and each sensor, be sure to check that the normal display is output in the Test Mode inspection and in DTC output inspection after installing all the parts.
3. DTC PRECAUTION Warnings for some DTCs cannot be cleared only by repairing the malfunctioning parts. If the warning is displayed after repair work, the DTC should be cleared after turning the engine switch off. NOTE: If a part is still malfunctioning even after the DTC is cleared, the DTC will be stored again.
4. CHASSIS DYNAMOMETER PRECAUTION Disable TRAC and VSC control when using a chassis dynamometer. When testing with 2-wheel drum tester such as a speedometer tester, a combination tester for the speedometer and brake, a chassis dynamometer, or when jacking up the rear wheels and turning the wheels, enter the Maintenance Mode with the Techstream and turn traction control off mode and the VSC system off mode. WARNING: For safety, secure the vehicle with restraint chains while using a drum tester. If the vehicle is tested in normal mode on the drum tester, the traction control and VSC system may cause the vehicle to jump out from the drum tester. NOTE: Check that the SLIP indicator light illuminates on the combination meter.
5. CAN COMMUNICATION SYSTEM PRECAUTION The CAN communication system is used for the data communication between the skid control ECU, the steering sensor, the yaw rate sensor (acceleration sensor included) and other ECUs. If there is trouble with the CAN communication line, corresponding DTCs in the communication line will be output. If the DTC in the CAN communication line is output, repair the malfunction in the communication line and troubleshoot the Electronically Controlled Brake System while data communication is normal. Since the CAN communication line has a specific length and route, it cannot be repaired temporarily with a bypass wire, etc.

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1. VDIM (Vehicle Dynamics Integrated Management) DESCRIPTION This vehicle is equipped with VDIM. It is a concept of vehicle motion control that integrates brake control, drive force control and steering control. Conventional vehicles use a combination of independent functions such as ABS, TRAC, VSC, electronic power steering and variable gear ratio steering. However VDIM integrates these systems to improve "driving, turning and stopping", the motion performance of the vehicle in other words. In conventional vehicles, control starts at the limit of the vehicle. However VDIM exercises control before the limit is reached, creating a smooth vehicle response. This expands the limits of the vehicle, and increases driving pleasure. The VDIM manages all functions, such as the ABS with EBD, brake assist, the TRAC, and the VSC. It is operated by the Electronically Controlled Brake System, which regulates brake fluid pressure. The steering cooperative control function is also available. Thus the VDIM is able to perform comprehensive management. Conventional brake control systems begin to control either the braking or motive force in order to stabilize the vehicle motion when it becomes unstable due to loss of tire traction. In contrast, in order to maintain stable vehicle control, the VDIM commences controlling the brake and steering systems in accordance with changes in balance before the vehicle becomes unstable. As a result, smooth vehicle control is achieved. Conventional brake control systems manage all related functions, such as the ABS with EBD, brake assist, the TRAC and the VSC independently, according to the vehicle dynamics. In contrast, the VDIM provides smooth control by seamlessly integrating all those functions.
2. ELECTRONICALLY CONTROLLED BRAKE SYSTEM DESCRIPTION The system detects the degree of brake pedal operation with a brake pedal stroke sensor and two master cylinder pressure sensors, and calculates the optimum hydraulic brake force. The hydraulic pressure source is adjusted based on this so that the optimum hydraulic control is independently performed on all four wheels. Meanwhile, the Electronically Controlled Brake System performs control of the normal brakes, ABS, TRAC, VSC and brake assist in accordance with the operations of the driver. There is a hydraulic backup mechanism that applies master cylinder pressure generated by human power to the wheel cylinder when the brake control stops. In addition, as a fail-safe mechanism, when the brake control is malfunctioning, the system excludes the malfunctioning sections and continues to perform brake control on the normal sections. A power backup unit (brake control power supply) is also used to ensure a stable supply of power to the system.
3. FUNCTION DESCRIPTION HINT: The yaw rate sensor and acceleration sensor are combined in a single unit. This unit communicates with the skid control ECU via CAN communication. ABS (Anti-lock Brake System) The ABS helps prevent the wheels from locking when the brakes are applied suddenly and firmly or applied on a slippery surface. Operation description The skid control ECU detects the wheel lock condition by receiving vehicle speed signals from each speed sensor, and sends control signals to the solenoid valve. The solenoid valve avoids wheel lock by controlling the oil pressure of each wheel cylinder. The ABS warning light comes on when the ABS system is malfunctioning. EBD (Electronic Brake Force Distribution) The EBD control utilizes the ABS, performing proper brake force distribution between the front and rear wheels in accordance with driving conditions. When braking while cornering, it also controls the brake forces of the right and left wheels, helping to maintain proper vehicle control. Operation description The skid control ECU receives the speed signal from each speed sensor to detect the slip condition of the wheels and sends the control signal to the solenoid. The solenoid valve controls the oil pressure of each wheel cylinder and splits the control power properly between the front and rear wheels and the right and left wheels. The ABS and BRAKE warning lights come on to indicate a malfunction in the EBD system. BA (Brake Assist) The primary purpose of the brake assist system is to provide auxiliary brake force to assist a driver who cannot generate a brake force large enough during emergency braking, thus helping to maximize the vehicle's brake performance. Operation description The skid control ECU receives the brake pedal stroke sensor signal and the oil pressure signal from the master cylinder pressure sensor to determine whether brake assist is necessary or not. If brake assist is deemed necessary, the skid control ECU will send control signals to the solenoid. The solenoid valve then control the pressure applied to each wheel cylinder. The ABS warning light comes on to indicate a malfunction in the BA system. Regarding changing of TRAC and VSC operation permission / disablement through VSC OFF switch Changing modes Through the VSC OFF switch, the vehicle can be changed to normal mode, TRAC OFF mode and VSC OFF mode. Normal mode When the vehicle is in TRAC OFF mode or VSC OFF mode, and the VSC OFF switch is pressed for a short amount of time, the vehicle changes to normal mode. During normal mode, TRAC and VSC operation is possible. After the engine switch is turned on (IG), the vehicle is in normal mode. TRAC OFF mode When the vehicle is in normal mode and the VSC OFF switch is pressed for a short amount of time, the vehicle changes to TRAC OFF mode. During TRAC OFF mode, the TRAC OFF message will be displayed on the multi-information display, and TRAC operation is disabled. During TRAC OFF mode, if the vehicle speed increases, the vehicle automatically returns to normal mode. VSC OFF mode When the vehicle is stopped and the VSC OFF switch is pressed for 3 seconds or more, the vehicle changes to VSC OFF mode. During VSC OFF mode, the VSC OFF indicator light will come on and the TRAC OFF message will be displayed on the multi-information display. Also, VSC and TRAC operation is disabled. During VSC OFF mode, even if the vehicle speed increases, the vehicle does not return to normal mode. TRAC (Traction Control) The TRAC system helps prevent the drive wheels from slipping when the driver depresses the accelerator pedal excessively while starting off or accelerating on a slippery surface. Operation description The skid control ECU detects vehicle's slip condition by receiving signals from each speed sensor and ECM via CAN communication. The skid control ECU controls engine torque with the ECM via CAN communication and oil pressure through the solenoid valve. The SLIP indicator light blinks when the system is operating. When there is a malfunction in the TRAC system, the brake control warning light and SLIP indicator light come on. The VSC OFF switch stops traction control operation. HINT: When the VSC OFF switch is pressed for a short amount time, the vehicle changes to TRAC OFF mode, and TRAC operation is disabled. During TRAC OFF mode, if the VSC OFF switch is pressed again or the vehicle speed increases to 50 km/h (13.8 mph) , TRAC operation becomes possible. During TRAC OFF mode, the TRAC OFF message will be displayed on the multi-information display. VSC (Vehicle Stability Control) The VSC system helps prevent the vehicle from slipping sideways as a result of strong front or rear wheel skid during cornering. Operation description The skid control ECU determines vehicle condition by receiving signals from the speed sensor, yaw rate and acceleration sensor and steering angle sensor. The skid control ECU controls engine torque with the ECM via CAN communication, and brake fluid pressure with the solenoid valve. The SLIP indicator light blinks and the skid control buzzer sounds when the system is operating. When there is a malfunction in the VSC system, the brake control warning light and SLIP indicator light come on. The VSC OFF switch stops VSC operation. HINT: When the VSC OFF switch is pressed for 3 seconds or more with the vehicle stopped, the VSC system changes to VSC OFF mode. If the VSC OFF switch is pressed again with the system in VSC OFF mode, the TRAC and VSC systems can be operated. When the system is in VSC OFF mode, the VSC OFF indicator light will come on and the TRAC OFF message will be displayed on the multi-information display.
4. STEERING COOPERATION CONTROL The VDIM system effects coordinated control consisting of the Electronically Controlled Brake System, EPS (Electric Power Steering), and VGRS (Variable Gear Ratio Steering). By integrating these preventive safety functions, the VDIM system ensures higher driving stability and maneuverability performance. If the vehicle loses stability due to a slippage, this function effects brake control by applying hydraulic pressure to the wheels. At the same time, the EPS provides steering torque assist control or active steering wheel angle control and the VGRS provides variable gear ratio steering control to facilitate the driver's steering control.
5. HILL-START ASSIST CONTROL The hill-start assist control detects the sliding of the vehicle. It automatically increases the brake hydraulic pressure for the four wheels in order to reduce the reversing speed of the vehicle. The vehicle tends to slide backward when the driver moves his foot from the brake pedal to the accelerator pedal when trying to start on a steep or slippery uphill. This function is effective in this kind of situation in which starting is difficult.
6. DYNAMIC RADAR CRUISE CONTROL When a greater deceleration than usual is required while driving in vehicle control mode, braking force is generated by the brake hydraulic pressure control in accordance with the signal from the distance control ECU.
7. PRE-COLLISION CONTROL The pre-collision system predicts frontal collisions with other vehicles or obstructions. By winding up the seat belts prior to collision, and performing brake control and brake assist control, it lessens the impact during the collision. The extremely high frequency radar recognizes if there is a vehicle or obstruction on the road ahead, and the distance control ECU makes a judgment from the position of the object, the speed and the road surface of whether or not a collision is unavoidable. The distance control ECU sends this information via CAN communication to the seat belt control ECU, suspension control ECU and skid control ECU to operate each control element of the pre-collision system.
8. FUNCTION OF COMPONENTS Components Functions Skid control ECU Processes the signals from each sensor to perform brake control for ABS, TRAC, and VSC. In addition, it communicates with the ECM to output a control signal. ABS MAIN relay Controlled by the skid control ECU. In addition to supplying power to each solenoid, it supplies power to the skid control ECU. ABS MOTOR relay Controlled by the skid control ECU. Supplies power to the pump motor. Speed sensor (semiconductor type) Detects the wheel speed and inputs the results to the skid control ECU. Stop light switch Detects the brake operating conditions and inputs the results to the skid control ECU. It supplies power to the skid control ECU. Brake pedal stroke sensor Detects the brake pedal stroke volume and inputs the results to the skid control ECU. Brake control power supply Provides the system with a supplementary power supply by discharging the electric charge of the capacitor. When the vehicle power voltage (12 V) is low and an electric charge is accumulated in the power back up unit's capacitor, the electric charge is discharged. Skid control buzzer Sounds intermittently to inform the driver that the VSC is active. Sounds continuously to warn the driver of a reduction in accumulator hydraulic pressure in the brake actuator, an abnormality in the power supply system, or a reduction in the vehicle power voltage (12 V). ECM Controls the engine output during the operation of the TRAC and VSC by communicating with the skid control ECU. Yaw rate and acceleration sensor Detects the yaw rate (axial rotation) and the forward, rearward and lateral acceleration, and inputs the results to the skid control ECU. Steering angle sensor Detects the steering angle and direction, and outputs the results to the skid control ECU via CAN communication. Master cylinder Generates pressure in accordance with the force of the brake operation. Brake fluid reservoir Stores brake fluid for the master cylinder system and power supply system. Brake fluid level warning switch Detects a reduction in the level of the brake fluid in the reservoir. Stroke simulator Generates a natural pedal stroke in accordance with the pedal force of the driver during system operation (integrated with the master cylinder). Stroke simulator cut valve (SCSS) Sends brake fluid pressure generated in master cylinder to stroke simulator during system control. Brake actuator Controls the hydraulic pressure of each of the four wheel cylinders using the output signal of the skid control ECU. Pump motor Pumps up the brake fluid from the reservoir and supplies the accumulator with high hydraulic pressure. Accumulator Accumulators for the power supply system the hydraulic pressure generated by the pump. Accumulator pressure sensor (PACC) Built into the brake actuator to detect the accumulator hydraulic pressure. Relief valve Prevents excessive high pressure in the power supply system. It relieves the system by sending brake fluid to the reservoir when the pump has operated continuously, for example, during an accumulator hydraulic pressure sensor malfunction. Master cylinder pressure sensor (PMC1, PMC2) Built into the brake actuator to detect the pressure of the master cylinder and inputs the results to the skid control ECU. Wheel cylinder pressure sensor (PFR, PFL, PRR, PRL) Built into the brake actuator to detect the brake hydraulic pressure of each wheel cylinder. Switching solenoid valve (SMC1, SMC2) Switches the brake hydraulic pressure route according to whether normal brakes are used, or VDIM (ABS, TRAC and VSC) control are used. Linear solenoid valve (SLA##, SLR##) Controls the wheel cylinder hydraulic pressure during normal brake operation, and VDIM (ABS, TRAC and VSC) control. SLA## are solenoids for controlling pressure increases, and SLR## are solenoids for controlling pressure decreases. ABS warning light Comes on to inform the driver that a malfunction in the ABS or BA has occurred. Blinks to output DTC. BRAKE warning light Comes on to inform the driver that the parking brake is on when the system is normal or the brake fluid has decreased. Brake control warning light Comes on to inform the driver that a malfunction in the Electronically Controlled Brake System has occurred. SLIP indicator light Blinks to inform the driver that TRAC and VSC are operating. Comes on to inform the driver that a malfunction in the TRAC and/or VSC has occurred. Blinks to output DTCs. VSC OFF indicator light Comes on to inform the driver when the VSC off mode is entered using the VSC OFF switch. Multi-information display Shows warning messages to alert the driver when the skid control ECU detects malfunctions in the brake control system. Displays to inform the driver when the TRAC off mode is entered using the VSC OFF switch.
9. FAIL-SAFE When a failure occurs in the ABS with BA, TRAC and VSC systems, the ABS warning, brake control warning and SLIP indicator lights will come on and ABS with BA, TRAC and VSC operations will be prohibited. In addition to this, when there is a failure that disables the EBD operation, the BRAKE warning light also comes on and the EBD operation is prohibited. If control is prohibited due to a malfunction during operation, control will be disabled gradually. This is done to avoid sudden vehicle instability.
10. INSPECTION MODE VSC operation can be disabled by operating the Techstream. HINT: Refer to the Techstream operator's manual for further details.

FREEZE FRAME DATA

1. FREEZE FRAME DATA If a DTC is detected when the ABS, BA, TRAC or VSC operates, the skid control ECU stores the current vehicle (sensor) state as Freeze Frame Data. The skid control ECU stores the number of times (maximum: 31) the engine switch has been turned from off to on (IG) since the last time the ABS, BA, TRAC or VSC was activated. HINT: The skid control ECU will not count the number of times the engine switch is turned on (IG) if the vehicle does not drive at the speed of at least 7 km/h (4.3 mph), or a DTC is detected. Freeze Frame Data at the time the ABS, BA, TRAC or VSC operates: The skid control ECU stores and updates the data whenever the ABS, BA, TRAC or VSC system operates. When the ECU stores data at the time a DTC is detected, the data stored when the ABS, BA, TRAC or VSC operated may be erased. Freeze Frame Data at the time a DTC is detected: When the skid control ECU stores data at the time a DTC is detected, no updates will be performed until the data is cleared. Connect the Techstream to the DLC3. Turn the engine switch on (IG). From the display on the tester, select the Freeze Frame Data. ABS / VSC / TRAC: Tester Display Measurement Item Reference Value Detailed Freeze DTC Detailed code for freeze frame DTC Min.: 0, Max.: 65535 Elapsed Time after Freeze Trigger Elapsed time after freeze trigger Min.: 0 ms, Max.: 500 ms Number of IG ON Number of operations of engine switch on (IG) after storing Freeze Frame Data 0 to 31 Elapsed Time Elapsed time after engine switch on (IG) Min.: 0 sec., Max.: 100661.76 sec. Buzzer Skid control buzzer signal Skid control buzzer ON: ON, OFF: OFF Stop Light SW Stop light switch signal Stop light switch ON: ON, OFF: OFF Parking Brake SW Parking brake switch signal Parking brake switch ON: ON, OFF: OFF TRC / VSC Off Mode TRAC / VSC off mode Normal mode TRAC off mode VSC off mode Reservoir Warning SW Brake fluid level warning switch signal Brake fluid level warning switch ON: ON, OFF: OFF Gear Position Gear position information FAIL 1st 2nd 3rd 4th 5th 6th 7th 8th P, N R NOT R Shift Lever Position Shift lever position information FAIL 1st 2nd 3rd 4th 5th 6th/B D/M P, N R Operated System Operated system status ABS activated: ABS VSC activated: VSC TRAC activated: TRC BA activated: BA PBA activated: PBA PB activated: PB Hill-start assist control activated: HA-CTRL Fail-safe mode activated: FAIL System prohibited: SYS No system activated: NON Master Cylinder Sensor Master cylinder pressure sensor reading Brake pedal released: 0.3 to 0.9 V Brake pedal depressed: 0.8 to 4.5 V M/C Sensor Grade Master cylinder pressure sensor change Min.: -30 MPa/s, Max.: 225 MPa/s Master Cylinder Sensor 2 Master cylinder pressure sensor reading Min.: 0 V, Max.: 5 V Stroke Sensor Stroke sensor reading Min.: 0 V, Max.: 5 V Stroke Sensor 2 Stroke sensor 2 reading Min.: 0 V, Max.: 5 V Accumulator Sensor Accumulator pressure sensor reading Min.: 0 V, Max.: 5 V Yaw Rate Sensor Yaw rate sensor reading Min.: -128 deg/s, Max.: 127 deg/s FR W/C Sensor FR wheel cylinder pressure sensor reading Min.: 0 V, Max.: 5 V FL W/C Sensor FL wheel cylinder pressure sensor reading Min.: 0 V, Max.: 5 V RR W/C Sensor RR wheel cylinder pressure sensor reading Min.: 0 V, Max.: 5 V RL W/C Sensor RL wheel cylinder pressure sensor reading Min.: 0 V, Max.: 5 V Lateral G Lateral G Min.: -25.11 m/s 2 , Max.: 24.91 m/s 2 Forward and Rearward G Forward and rearward G Min.: -25.11 m/s 2 , Max.: 24.91 m/s 2 FR Wheel Speed FR wheel speed reading Min.: 0 km/h (0 mph), Max.: 326.4 km/h (202 mph) FL Wheel Speed FL wheel speed reading Min.: 0 km/h (0 mph), Max.: 326.4 km/h (202 mph) RR Wheel Speed RR wheel speed reading Min.: 0 km/h (0 mph), Max.: 326.4 km/h (202 mph) RL Wheel Speed RL wheel speed reading Min.: 0 km/h (0 mph), Max.: 326.4 km/h (202 mph) Vehicle Speed Vehicle speed reading Min.: 0 km/h (0 mph), Max.: 326.4 km/h (202 mph) FR Wheel Direction Front right wheel direction signal Front right wheel direction FORWARD: Forward, BACK: Back FL Wheel Direction Front left wheel direction signal Front left wheel direction FORWARD: Forward, BACK: Back RR Wheel Direction Rear right wheel direction signal Rear right wheel direction FORWARD: Forward, BACK: Back RL Wheel Direction Rear left wheel direction signal Rear left wheel direction FORWARD: Forward, BACK: Back Real Engine Torque Real engine torque Min.: -1024 N*m, Max.: 1023 N*m Accelerator Opening Angle % Accelerator opening angle % Min.: 0%, Max.: 128% ECB* Motor Relay ABS motor relay signal ABS motor relay ON: ON, OFF: OFF ECB* Motor Relay 2 ABS motor relay 2 signal ABS motor relay 2 ON: ON, OFF: OFF ECB* Main Relay ABS main relay signal ABS main relay ON: ON, OFF: OFF ECB* Main Relay 2 ABS main relay 2 signal ABS main relay 2 ON: ON, OFF: OFF ECB* Solenoid (SMC1) Master cut solenoid (SMC1) signal Master cut solenoid (SMC1) ON: ON, OFF: OFF ECB* Solenoid (SMC2) Master cut solenoid (SMC2) signal Master cut solenoid (SMC2) ON: ON, OFF: OFF ECB* Solenoid (SCSS) Stroke simulator solenoid (SCSS) signal Stroke simulator solenoid (SCSS) ON: ON, OFF: OFF Capacitor Mode Capacitor mode Capacitor mode ON: ON, OFF: OFF IG1 Voltage Value IG1 voltage value Min.: 0 V, Max.: 20 V IG2 Voltage Value IG2 voltage value Min.: 0 V, Max.: 20 V BS1 Voltage Value BS1 voltage value Min.: 0 V, Max.: 20 V BS2 Voltage Value BS2 voltage value Min.: 0 V, Max.: 20 V VM1 Voltage Value VM1 voltage value Min.: 0 V, Max.: 20 V VM2 Voltage Value VM2 voltage value Min.: 0 V, Max.: 20 V +B1 Voltage Value +B1 voltage value Min.: 0 V, Max.: 20 V +B2 Voltage Value +B2 voltage value Min.: 0 V, Max.: 20 V Motor Relay Voltage Value Motor relay voltage value Min.: 0 V, Max.: 20 V SLAFR Solenoid Current SLAFR solenoid current Min.: 0 A, Max.: 1.5 A SLAFL Solenoid Current SLAFL solenoid current Min.: 0 A, Max.: 1.5 A SLARR Solenoid Current SLARR solenoid current Min.: 0 A, Max.: 1.5 A SLARL Solenoid Current SLARL solenoid current Min.: 0 A, Max.: 1.5 A SLRFR Solenoid Current SLRFR solenoid current Min.: 0 A, Max.: 1.5 A SLRFL Solenoid Current SLRFL solenoid current Min.: 0 A, Max.: 1.5 A SLRRR Solenoid Current SLRRR solenoid current Min.: 0 A, Max.: 1.5 A SLRRL Solenoid Current SLRRL solenoid current Min.: 0 A, Max.: 1.5 A FR Target Oil Pressure FR wheel target oil pressure reading Min.: 0 MPa, Max.: 20 MPa FL Target Oil Pressure FL wheel target oil pressure reading Min.: 0 MPa, Max.: 20 MPa RR Target Oil Pressure RR wheel target oil pressure reading Min.: 0 MPa, Max.: 20 MPa RL Target Oil Pressure RL wheel target oil pressure reading Min.: 0 MPa, Max.: 20 MPa Steering Angle Sensor Steering angle sensor reading Left turn: Increase Right turn: Drop *: Electronically Controlled Brake

FAIL-SAFE CHART

1. FAIL-SAFE OPERATION When trouble occurs in the brake control system, the skid control ECU turns the warning light on, and prohibits ABS, BA, and VSC operations. The skid control ECU prevents operation of a malfunctioning hydraulic pressure system and continues brake control with the normal hydraulic pressure system. HINT: If control of the Electronically Controlled Brake System for any of the 4 wheels is prohibited, that wheel loses brake booster function or braking ability. If one of the 4 wheels loses brake booster function, the feeling when depressing the brake pedal changes as the stroke simulator (pedal reactive force generating solenoid) operation will be prohibited. If control of the Electronically Controlled Brake System for all wheels is prohibited, the 2 front wheels will lose brake booster function. ABS, EBD AND BA SYSTEM: Malfunction Area Control Method ABS system ABS, BA, TRAC and VSC control prohibited BA system ABS, BA, TRAC and VSC control prohibited EBD system ABS, EBD, BA, TRAC and VSC control prohibited TRAC AND VSC SYSTEM: Malfunction Area Control Method Engine control system (TRAC and VSC systems) Before control: Disables control During control: Uses only the brakes to effect control Brake control system (TRAC and VSC systems) Before control: Disables control During control: Disables control (by gradually ending control) HINT: As for the TRAC and VSC systems, different systems prohibit different controls depending on a malfunctioning part.