Brake Control: Other Lexus IS II

PRECAUTION

Note. When disconnecting the battery terminal, initialize the following system after the terminal is reconnected

SYSTEM PROCEDURE REFERENCE

HINT

See the table below to check if the vehicle is equipped with VDIM.

PARTS AND SYSTEM REFERENCE

1. TROUBLESHOOTING PRECAUTIONS When there is a malfunction with terminal contact points or part installation problems, 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 the system may be influenced by malfunctions in systems other than the brake control system, be sure to check for DTCs in other systems.
2. HANDLING PRECAUTIONS Do not remove or install the VSC parts such as the steering angle sensor or yaw rate sensor (acceleration sensor included) except when required, as they cannot be adjusted correctly after removal or installation. Be sure to perform preparation before work and confirmation after work is completed by following the direction in the repair information when working on the VSC 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. When removing and installing the ECU, actuator and each sensor, be sure to check that the normal display is output in 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 DTC for a malfunctioning part reappears after it has been cleared, then it has been stored again.
4. CHASSIS DYNAMOMETER PRECAUTION Change to Test Mode to disable TRAC and VSC control when using a chassis dynamometer. HINT: The vehicle may move unexpectedly out of the dynamometer because of TRAC and VSC operations. Pressing the traction OFF switch (2WD only) does not disable TRAC operation completely. NOTE: Make sure that the VSC warning (multi information display and master caution indicator light) light is blinking (move to Test Mode). Secure the vehicle with the lock chain for safety.
5. CAN COMMUNICATION SYSTEM PRECAUTIONS The CAN communication system is used for the data communication between the skid control ECU, the steering angle 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 are output. If the DTC in the CAN communication line is output, repair the malfunction in the communication line and troubleshoot the VSC system while data communication is normal. Since the CAN communication line has its own length and route, it cannot be repaired temporarily with the bypass wire, etc.

Scheme 170

Scheme 171

Scheme 172

Scheme 173

SIGNAL COMMUNICATION

Scheme 174

Scheme 175

Scheme 176

Scheme 177

Scheme 178

1. FUNCTION DESCRIPTION HINT: The skid control ECU is located within the brake actuator assembly. The yaw rate sensor and acceleration sensor are combined in a single unit. This unit communicates with the skid control ECU through CAN communication. ABS (Anti-lock Brake System) The ABS helps prevent the wheels from locking when the brakes are applied firmly or when braking on a slippery surface. Operation description The skid control ECU detects wheel lock condition by receiving vehicle speed signals from each speed sensor, and sends control signals to the pump motor and solenoid valve. The pump motor and solenoid valve avoid wheel lock by controlling the brake fluid 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 ABS, and performs 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 vehicle behavior. Operation description The skid control ECU receives the speed signals from each speed sensor to detect the slip condition of the wheels and sends the control signals to the solenoid. The solenoid valve controls the fluid pressure of each wheel cylinder and splits the control power properly between the front and rear wheels and the right and left wheels. The BRAKE warning light comes 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 the driver who cannot generate a large enough brake force during emergency braking, thus helping to maximize the vehicle's brake performance. Operation description The skid control ECU receives the speed signal from each speed sensor and the fluid pressure signal from the master cylinder pressure sensor to determine whether brake assist is necessary. If brake assist is necessary, the skid control ECU sends control signals to the pump motor and solenoid. The pump and 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. TRAC (Traction Control) The TRAC system helps prevent the drive wheels from slipping when the driver presses down on the accelerator pedal excessively when starting off or accelerating on a slippery surface. Operation description The skid control ECU detects the 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 pump and solenoid valve. The SLIP indicator light blinks when the system is operating. When there is a malfunction in the TRAC system, both master caution and SLIP indicator lights will come on and the DTC will be displayed on the multi information display. Traction OFF switch stops traction control operation (2WD only). 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 the 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 fluid pressure with the pump and 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, both master caution and SLIP indicator lights will come on and the DTC will appear on the multi information display.
2. HILL-START ASSIST CONTROL (A/T) The hill start assist control detects rearward motion of the vehicle. It automatically increased the brake hydraulic pressure for the four wheels in order to reduce the rearward speed of the vehicle. The vehicle tends to slide backward when the driver moves his foot from the brake pedal to the accelerator pedal trying to start on a steep or slippery uphill. This function is effective in this kind of situation in which starting is difficult. After a maximum of 5 seconds, fluid pressure is gradually released and control will be completed.
3. DYNAMIC RADAR CRUISE CONTROL (A/T) 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.
4. PRE-COLLISION CONTROL (A/T) 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 judgement on whether a collision is unavoidable from the position of the object, the speed and the road surface. The distance control ECU sends this information via a 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.
5. ABS with EBD, BA, TRAC and VSC OPERATION The skid control ECU calculates vehicle stability tendency based on the signals from the speed sensor, yaw rate and acceleration sensor and steering angle sensor. In addition, it evaluates the results of the calculations to determine whether any control actions (control of the engine output torque by electronic throttle control and of the wheel brake pressure by the brake actuator assembly) should be implemented. The SLIP indicator blinks and the skid control buzzer sounds to inform the driver that the VSC system is operating. The SLIP indicator also blinks when traction control is operating, and the operation being performed is displayed.
6. FAIL SAFE When a failure occurs in the ABS with BA, TRAC and VSC systems, the ABS and VSC warning lights, and SLIP indicator light come on and ABS with BA, TRAC and VSC operations are 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 to avoid sudden vehicle instability.
7. INITIAL CHECK When the vehicle speed first becomes approximately 4 mph (6 km/h) or more after the engine switch is turned on (IG), each solenoid valve and motor of the brake actuator is sequentially activated to perform an electrical check. During the initial check, the operating sound of solenoid valve and motor can be heard from the engine compartment, but this is not a malfunction.
8. SERVICE MODE VSC operation can be disabled by operating the intelligent tester. HINT: Refer to the intelligent tester operator's manual for further details.
9. FUNCTION OF COMPONENTS FUNCTION OF COMPONENTS Components Function Speed sensor (Semiconductor type) Detects the wheel speed and sends the signal to the skid control ECU. Skid control ECU (housed in brake actuator assembly) Processes the signals sent from each sensor to control the ABS, BA, TRAC, and VSC. Sends and receives the control signals to or from the ECM, yaw rate and acceleration sensor, and steering angle sensor, etc. via CAN communication. Brake actuator assembly Consists of the master cylinder cut solenoid valve, retention solenoid valve, pressure reduction solenoid valve, pump motor, and reservoir, and adjusts the brake fluid pressure applied to each wheel cylinder. Houses the skid control ECU. Solenoid relay Supplies power to each solenoid. Housed in the skid control ECU. Motor relay (ABS MOTOR2 relay) Supplies power to the pump motor. Fail safe relay (ABS MOTOR1 relay) Cuts off power to the motor when the pump motor circuit malfunctions. Steering angle sensor Installed in the combination switch. Detects the steering amount and direction and sends the signals to the skid control ECU via CAN communication. Has the magnetic resistance element which detects the rotation of the magnet housed in the detection gear in order to detect the changes of magnetic resistance and the steering amount and direction. Yaw rate and acceleration sensor Acceleration sensor measures the capacity of the condenser that changes the distance between the electrodes depending on G force, which occurs when the vehicle is accelerated, and converts the measured value into electrical signals. Yaw rate sensor detects the vehicle's angular velocity (yaw rate) in the vertical direction based on the amount and direction of the piezoelectric ceramics deflection. Sends signals to the skid control ECU via CAN communication. Master cylinder pressure sensor Detects the fluid pressure in the master cylinder. Housed in the brake actuator assembly. Stop light switch Detects the brake operating conditions and inputs the results to the skid control ECU. Brake pedal load sensing switch Installed on the brake pedal. Turned on when the brake pedal is depressed. ECM Controls the engine output when TRAC and VSC are operating with the skid control ECU via CAN communication. Skid control buzzer Intermittently sounds to inform the driver that the VSC is operating. 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, the brake fluid has decreased, or the master cylinder pressure is lost as the brake pedal load sensing switch is pressed. Comes on to inform the driver that a malfunction in the EBD has occurred. SLIP indicator light Blinks to inform the driver that TRAC and VSC are operating. (In the case of a 4WD vehicle, the SLIP indicator light blinks even while TRAC and VSC are operating. In the case of a 2WD vehicle, the indicator light comes on when a malfunction is detected.) Comes on when the traction OFF switch is OFF to inform the driver of the traction control prohibited state (2WD only) or malfunction in the TRAC and VSC system occurred. VSC warning light (Multi information display) Displays to inform the driver that a malfunction in the VSC system has occurred. Displays to output DTC. Master caution indicator light Comes on to inform the driver that a malfunction.

FREEZE FRAME DATA

1. FREEZE FRAME DATA Whenever an ABS DTC is detected, 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 was activated. HINT: However, if the vehicle is stopped or at low speed (4.3 mph (7 km/h) or less), or if a DTC is detected, the skid control ECU will stop counting the number. Freeze Frame Data at the time the ABS operates: The skid control ECU stores and updates data whenever the ABS system operates. When the ECU stores data at the time a DTC is detected, the data stored during ABS operation is 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 intelligent tester to the DLC3. Turn the engine switch on (IG). From the display on the tester, select the Freeze Frame Data. ITEM REFERENCE CHART Item (Display) Measurement Item Reference Value VEHICLE SPD Vehicle speed reading Min.: 0 mph (0 km/h), Max.: 202 mph (326.4 km/h) STOP LAMP SW Stop light switch signal Stop light switch ON: ON, OFF: OFF #IG ON Number of operations of engine switch on (IG) after storing freeze frame data 0 to 31 MAS CYL PRESS 1 Master cylinder pressure sensor reading Brake pedal released: 0.3 to 0.5 V M/C PRESS GRADE Master cylinder pressure sensor change Min.: -30 MPa/s, Max.: 225 MPa/s YAW RATE Yaw rate sensor reading Min.: -128 deg/s, Max.: 127 deg/s STEERING SEN Steering angle sensor reading Left turn: Increase Right turn: Drop FORWARD&REA G Forward and backward G Min.: -25.11 m/s 2 , Max.: 24.91 m/s 2 SPD GRADE Vehicle speed grade Min.: -25.11 m/s 2 , Max.: 24.91 m/s 2 BUZZER Skid control buzzer signal Skid control buzzer ON: ON, OFF: OFF ACCELERATOR % Accelerator opening angle % Min.: 0 %, Max.: 128 % PARKING BRAKE SW Parking brake switch signal Parking brake switch ON: ON, OFF: OFF FR WHEEL DIR FR wheel direction signal Front right wheel direction FORWARD: Forward, BACK: Back FL WHEEL DIR FL wheel direction signal Front left wheel direction FORWARD: Forward, BACK: Back RR WHEEL DIR RR wheel direction signal Rear right wheel direction FORWARD: Forward, BACK: Back RL WHEEL DIR RL wheel direction signal Rear left wheel direction FORWARD: Forward, BACK: Back ENGINE TORQUE Real engine torque Min.: -1024 Nm, Max.: 1023 Nm FR WHEEL SPD FR wheel speed Min.: 0 mph (0 km/h), Max.: 202 mph (326.4 km/h) FL WHEEL SPD FL wheel speed Min.: 0 mph (0 km/h), Max.: 202 mph (326.4 km/h) RR WHEEL SPD RR wheel speed Min.: 0 mph (0 km/h), Max.: 202 mph (326.4 km/h) RL WHEEL SPD RL wheel speed Min.: 0 mph (0 km/h), Max.: 202 mph (326.4 km/h) LATERAL G Lateral G Min.: -25.11 m/s 2 , Max.: 24.91 m/s 2 GEAR POSITION Gear position information FAIL 1st 2nd 3rd 4th 5th 6th P, N R NOT R LEVER POSITION Shift lever position information FAIL 1st 2nd 3rd 4th 5th 6th/B D/M P, N R TRAC/VSC OFF SW (1) Traction OFF switch signal Traction OFF switch ON: OFF, OFF: ON BRK PEDAL SW Brake pedal load sensing switch signal Brake pedal load sensing switch ON: ON, OFF: OFF OPERATED SYSTEM Operated system status ABS activated: ABS VSC activated: VSC TRAC activated: TRAC BA activated: BA HAB activated: HAB PBA activated: PBA PB activated: PB HAC activated: HAC Fail safe mode activated: FAIL No system activated: NON System prohibited: SYS FREEZE TIME Elapsed time after freeze trigger Min.: 0 ms, Max.: 500 ms TROUBLE CODE Freeze frame DTC Displays to output DTC INSPECTION MODE Inspection mode Inspection mode OTHER: Normal, INSPECT: Service (1) 2WD

FAIL-SAFE CHART

1. FAIL SAFE OPERATION If there is a problem with sensor signals or actuator systems, the skid control ECU prohibits power supply to the brake actuator assembly and informs the ECM of VSC system failure. The brake actuator assembly turns off each solenoid and the ECM shuts off VSC control (traction control signal) from the skid control ECU accordingly, which turns out to be as if the ABS, TRAC and VSC systems were not installed. The ABS control will be prohibited, but EBD control continues as much as possible. If EBD control is impossible, the BRAKE warning light comes on to warn the driver (See «TERMINALS OF ECU»(ref-235572-S08116184342006062400000) ). If system components have any malfunction before starting control, immediately stop the operation. If system components have any malfunction during control, gradually stop the control so as not to trigger a sudden change in vehicle conditions. If it is impossible to control the systems, the warning light comes on to inform the driver of termination of the systems (See «TERMINALS OF ECU»(ref-235572-S08116184342006062400000) ). HINT: If the hydraulic brake booster encounters a malfunction, brake performance is gradually lost and ABS, BA, TRAC and VSC systems are prohibited. ABS, EBD and BA system: MALFUNCTION AREA CONTROL REFERENCE 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 HINT: A malfunction in either the ABS or BA system will result in an identical operation, with ABS, BA, TRAC and VSC system control prohibited. TRAC and VSC system: MALFUNCTION AREA CONTROL REFERENCE 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 (VSC system) Before control: Disables control During control: Uses only the engine to effect control Brake control system (TRAC system) 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.