ABS-ECU

By integrating ABS-ECU into the hydraulic unit, no wiring harness for sending drive signal of the solenoid valve and pump motor is required, assuring higher reliability.
By incorporating the G-sensor, no sensor harness is required, enhancing the reliability.
Self-diagnostic and memory functions are integrated into ABS-ECU. If any malfunction is detected by the self-diagnostic function, ABS-ECU activates a fail-safe function and illuminates the ABS warning lamp and brake warning lamp^*.

note *: The brake warning lamp is used as the EBD control warning lamp.
ABS-ECU detects vehicle speed from the signals of the wheel speed sensor and its incorporated G sensor, recognizes the wheel rotation status, estimates the wheel slip condition based on the preprogrammed algorithm, and then controls the solenoid valve in the hydraulic unit so that the wheels do not lock.

ABS fluid pressure control

ABS control cycle

The ABS-ECU calculates the speed and deceleration of each wheel based on the signals from the four wheel speed sensors and the G sensor incorporated in the ABS-ECU, and estimates the vehicle speed at that time.
When the brake pedal is depressed, the brake fluid pressure applied to the wheel cylinder increases, and the wheel speed decreases. When the difference between the wheel speed and vehicle speed increases, and the vehicle deceleration goes below the specified value (Point A), ECU determines that the wheels are about to be locked. At this time, ECU reduces the brake fluid pressure by outputting the pressure decrease signal to the solenoid valves (IN, OUT). (between a and b)
When the vehicle deceleration and wheel speed begin recovery, and the vehicle speed reaches the point B, ECU outputs the pressure hold signal to maintain the wheel cylinder fluid pressure. (between b and c)
When the wheel speed deceleration is further recovered and overpasses the point C, ECU determines that the wheel lock possibility has been eliminated and increases the brake fluid pressure by outputting the pressure increase signal again. (between c and d)
Brake fluid pressure is controlled by repeating the increase and hold of the pressure. (between d and e)
When the wheel deceleration goes below the threshold again, ABS-ECU controls the brake fluid pressure by repeating the cycle (Step 2 to 5).

Four-wheel control

EBD fluid pressure control

EBD control is activated in a range with lower slip ratio where ABS is disabled. EBD calculates vehicle deceleration and slip amount of the four wheels based on the wheel speed sensor signal. If the rear wheel speed differs from the vehicle speed by a certain level or more, EBD increases, holds, and decreases the pressure at the rear wheel control solenoid valve in the hydraulic unit, and then adjusts rear wheel brake fluid pressure fairly close to an ideal distribution curve.

INITIAL CHECK

ABS-ECU performs the following initial checks using the diagnostic functions. ABS-ECU illuminates the ABS warning lamp for 3 seconds (including the initial check) ^* after the ignition switch is turned ON. If any malfunction is detected, ABS-ECU continues illuminating the ABS warning lamp and disables ABS control.

note

^*: The ABS warning lamp may stay on after the ignition switch is turned ON until the startup vehicle speed reaches approximately 10 km/h. As far as ABS-ECU memorizes any diagnosis code related to the wheel speed sensor malfunction recorded during the previous ignition ON status, ABS-ECU continues illuminating the ABS warning lamp until it verifies that the malfunction for that code is resolved (startup check).

INITIAL CHECK

Performs self-diagnosis in ABS-ECU.

STARTUP CHECK

When the startup vehicle speed reaches approximately 10 km/h, ABS-ECU performs the following checks.
1.Motor, solenoid valve check (Initial startup^* only)
Turns ON the motor relay in ECU, and checks the pump motor operation. At the same time, ABS-ECU sequentially energizes each solenoid valve in a very short period and checks the valve operation.

note

^*: Initial startup indicates a first startup after the system has started.

2.Wheel speed sensor check
ABS-ECU checks for any wheels that have not received wheel speed sensor signal from the startup.

CONSTANT CHECK

ABS-ECU constantly checks the following items.
1.ABS-ECU
(1) Performs self-diagnosis in ECU.
(2) Checks for abnormal output voltage of G sensor, and detects open or short circuit in the G sensor.
(3) Checks the output voltage for G sensor, and determines that the G sensor is stuck when the output voltage exceeding the specification continues for a certain period or more.
2.ECU power supply
Checks if ECU power supply voltage stays within the operational range.
3.Wheel speed sensor
(1) Monitors the output voltage of the sensor signal wiring harness and checks for abnormal output voltage (open/short circuit).
(2) Checks for any wheels that do not send pulse signal while the vehicle is in motion.
(3) Checks if wheel speed which is abnormally higher or lower than the vehicle speed is input.
4.Pump motor, solenoid valve
Checks that the ABS-ECU output signal and the operating conditions of the pump motor and solenoid valve agree with each other.

CAN COMMUNICATION

ABS-ECU outputs the ABS warning lamp and the EBD warning lamp^* illumination request signals to the combination meter through CAN communication.

note

*: The brake warning lamp is used as EBD control warning lamp.

FAIL-SAFE FUNCTION

If any malfunction is detected by the self-diagnostic function, ABS-ECU illuminates the ABS warning lamp and brake warning lamp^*, and it disables ABS and EBD control.

note

*: The brake warning lamp is used as EBD control warning lamp.

Diagnosis code No.	Item		Countermeasures for failure
			EBD control	ABS control	Brake warning lamp	ABS warning lamp
C100A	Abnormality in FL wheel speed sensor circuit		Executed (Prohibited when two or more wheels are faulty.)	Prohibited	Extinguished^*2	Illuminated^*3
C1015	Abnormality in FR wheel speed sensor circuit
C1020	Abnormality in RL wheel speed sensor circuit
C102B	Abnormality in RR wheel speed sensor circuit
C1011	Abnormality in FL wheel speed sensor signal		Executed (Prohibited when two or more wheels are faulty.)	Prohibited	Extinguished^*2	Illuminated^*3
C101C	Abnormality in FR wheel speed sensor signal
C1027	Abnormality in RL wheel speed sensor signal
C1032	Abnormality in RR wheel speed sensor signal
C1014	Mutual monitoring of FL wheel speed sensor		Executed (Prohibited when two or more wheels are faulty.)	Prohibited	Extinguished^*2	Illuminated^*3
C101F	Mutual monitoring of FR wheel speed sensor
C102A	Mutual monitoring of RL wheel speed sensor
C1035	Mutual monitoring of RR wheel speed sensor
C1041	Abnormality in periodical signal for FL wheel speed sensor		Executed (Prohibited when two or more wheels are faulty.)	Prohibited	Extinguished^*2	Illuminated^*3
C1042	Abnormality in periodical signal for FR wheel speed sensor
C1043	Abnormality in periodical signal for RL wheel speed sensor
C1044	Abnormality in periodical signal for RR wheel speed sensor
C1046	FL wheel speed sensor control phase time exceeded		Executed (Prohibited when two or more wheels are faulty.)	Prohibited	Extinguished^*2	Illuminated^*3
C1047	FR wheel speed sensor control phase time exceeded
C1048	RL wheel speed sensor control phase time exceeded
C1049	RR wheel speed sensor control phase time exceeded
C104B	Abnormality in FL wheel inlet valve system		Prohibited	Prohibited	Illuminates	Illuminates
C104F	Abnormality in FR wheel inlet valve system
C1053	Abnormality in RL wheel inlet valve system
C1057	Abnormality in RR wheel inlet valve system
C105F	Abnormality in FL wheel outlet valve system		Prohibited	Prohibited	Illuminates	Illuminates
C1063	Abnormality in FR wheel outlet valve system
C1067	Abnormality in RL wheel outlet valve system
C105B	Abnormality in RR wheel outlet valve system
C2104	Malfunction of valve power supply circuit		Prohibited	Prohibited	Illuminates	Illuminates
C1073	Malfunction of motor drive circuit		Executed	Prohibited	Extinguished	Illuminated^*3
C2116	Abnormality in pump motor power supply voltage		Executed	Prohibited	Extinguished	Illuminated^*3
C1000	Abnormality in stop lamp switch circuit		Executed	Executed	Extinguished	Extinguished
C2200	Trouble in ABS-ECU		Prohibited	Prohibited	Illuminates	Illuminates
C2100	Battery voltage problem (low voltage)	9.7 ± 0.3 V or less^*1	Executed	Prohibited	Extinguished	Illuminates
		8.0 ± 0.5 V or less ^*1	Prohibited	Prohibited	Illuminates	Illuminates
C2101	Battery voltage problem (high voltage)	18.0 ± 1.0 V or more	Prohibited	Prohibited	Illuminates	Illuminates
C1395	Brake fluid charging incompletion		Executed	Executed	Extinguished	Flashes (1 Hz)
C2203	VIN not written		Executed	Executed	Extinguished	Illuminates
C1210	Defective G sensor	Abnormality in output voltage	Executed	Prohibited	Extinguished	Illuminates
C1242	Defective G sensor	Abnormality in output voltage	Executed	Prohibited	Extinguished	Illuminates
C2111	Sensor power supply circuit/Low input		Executed	Prohibited	Extinguished	Illuminates
C2112	Sensor power supply circuit/High input		Executed	Prohibited	Extinguished	Illuminates
C1608	Implausible diagnosis data		Executed	Executed	Extinguished	Extinguished
U0001	Bus off		Executed	Executed	Extinguished	Extinguished
U0100	Engine time-out error		Executed	Executed	Extinguished	Extinguished
U0114	4WD-ECU time-out error		Executed	Executed	Extinguished	Extinguished
U0141	ETACS time-out error		Executed	Executed	Extinguished	Extinguished
U1415	Variant coding not implemented		Executed	Prohibited	Extinguished	Illuminates
U1417	Invalid variant coding value (including wrong assembly)		Executed	Prohibited	Extinguished	Illuminates

note

^*1 This diagnosis code is not set within the vehicle speed of 20 km/h or less.
^*2 Turns ON when two or more wheels are faulty.
^*3 Stays ON until the vehicle speed reaches 10 km/h when the ignition switch is turned to ON next time.

DIAGNOSTIC FUNCTION

ABS-ECU has the following functions for easier system checks. The following items can be diagnosed using M.U.T-III.

Diagnosis code set
Service data output
Actuator test

DIAGNOSIS CODE SET

There are 48 diagnosis items. Since all the diagnostic results are recorded in volatile memory (EEPROM*), they are stored in the memory even though the battery terminals are disconnected.

note

*EEPROM (Electrical Erasable & Programmable ROM): Special type of memory that can be programmed or erased electrically
For each diagnosis item, refer to Workshop Manual.

SERVICE DATA OUTPUT

Using M.U.T-III, the input data sent from the sensors and switches can be read.

note

For service data items, refer to Workshop Manual.

ACTUATOR TEST

Using M.U.T-III, the actuators can be forcibly operated.

note

When ABS-ECU is disabled, the actuator test cannot be performed.
The actuator test can be performed only when the vehicle is stationary. When the vehicle speed reaches 10 km/h, the forcible actuator operation is disabled.
During actuator test, the ABS warning lamp flashes in 2Hz, and ABS control is prohibited.
For the actuator test specification, refer to Workshop Manual.