ABS System Description

ABS Modulator-Control Unit Inputs and Outputs for 25P Connector

Terminal number Wire color Terminal sign Description Measurement (Disconnect the ABS modulator-control unit 25P connector)
Terminal Conditions Voltage
1 WHT CAN-H F-CAN communication circuit ——— ——— ———
2 GRN FR +B Detects right-front wheel sensor signal ——— ——— ———
3 GRY^*1
RED^*2 FL-GND Detects left-front wheel sensor signal ——— ——— ———
5 PUR RL-GND Detects left-rear wheel sensor signal ——— ——— ———
6 LT GRN RR +B Detects right-rear wheel sensor signal ——— ——— ———
8 WHT FSR +B Power source for the fail-safe relay 8-GND At all times Battery voltage
9 RED MR +B Power source for the motor relay 9-GND At all times Battery voltage

Terminal number	Wire color	Terminal sign	Description	Measurement (Disconnect the ABS modulator-control unit 25P connector)
1	WHT	CAN-H	F-CAN communication circuit	———	———	———
2	GRN	FR +B	Detects right-front wheel sensor signal	———	———	———
3	GRY^1 RED^2	FL-GND	Detects left-front wheel sensor signal	———	———	———
5	PUR	RL-GND	Detects left-rear wheel sensor signal	———	———	———
6	LT GRN	RR +B	Detects right-rear wheel sensor signal	———	———	———
8	WHT	FSR +B	Power source for the fail-safe relay	8-GND	At all times	Battery voltage
9	RED	MR +B	Power source for the motor relay	9-GND	At all times	Battery voltage

*1: Except K20Z2 engine model
*2: K20Z2 engine model
*3: LHD type
*4: RHD type

Terminal number Wire color Terminal sign Description Measurement (Disconnect the ABS modulator-control unit 25P connector)
Terminal Conditions Voltage
10 LT BLU K-LINE Communications with HDS ——— ——— ———
12    ORN^*1
   WHT^*2 FL +B Detects left-front wheel sensor signal ——— ——— ———
14    BLU^*1
   YEL^*2 RL +B Detects left-rear wheel sensor signal ——— ——— ———
15    WHT^*1
   BLU^*2 RR-GND Detects right-rear wheel sensor signal ——— ——— ———
   16^*3    GRY^*1
   YEL^*2 IG1 Power source for activating the system 16-GND Ignition switch ON (II) Battery voltage
   16^*4 GRY
17 RED CAN-L F-CAN
communication circuit ——— ——— ———
18 PNK FR-GND Detects right-front wheel sensor signal ——— ——— ———
24 BLK GND Ground for the ABS modulator-control unit 24-GND At all times 0.1 V or less
25 BLK MR-GND Ground for the pump motor 25-GND At all times 0.1 V or less

Terminal number	Wire color	Terminal sign	Description	Measurement (Disconnect the ABS modulator-control unit 25P connector)
10	LT BLU	K-LINE	Communications with HDS	———	———	———
12	ORN^1 WHT^2	FL +B	Detects left-front wheel sensor signal	———	———	———
14	BLU^1 YEL^2	RL +B	Detects left-rear wheel sensor signal	———	———	———
15	WHT^1 BLU^2	RR-GND	Detects right-rear wheel sensor signal	———	———	———
16^*3	GRY^1 YEL^2	IG1	Power source for activating the system	16-GND	Ignition switch ON (II)	Battery voltage
16^*4	GRY
17	RED	CAN-L	F-CAN communication circuit	———	———	———
18	PNK	FR-GND	Detects right-front wheel sensor signal	———	———	———
24	BLK	GND	Ground for the ABS modulator-control unit	24-GND	At all times	0.1 V or less
25	BLK	MR-GND	Ground for the pump motor	25-GND	At all times	0.1 V or less

*1: Except K20Z2 engine model
*2: K20Z2 engine model
*3: LHD type
*4: RHD type

System Outline

This system is composed of the ABS modulator-control unit, the wheel sensors and system indicators in the gauge control module. The ABS modulator-control unit controls the anti-lock brake and the brake distribution function.

ABS Features

Without ABS, when the brake pedal is pressed while driving, the wheels sometimes lock before the vehicle comes to a stop. In such an event, the maneuverability of the vehicle is reduced if the front wheels are locked, and the stability of the vehicle is reduced if the rear wheels are locked, creating an extremely unstable condition. With ABS, the system precisely controls the slip rate of the wheels to ensure maximum grip force from the tyres, and it thereby ensures maneuverability and stability of the vehicle. The ABS calculates the slip rate of the wheels based on the four wheel speed, then it controls the brake fluid pressure to reach the target slip rate.

Grip force of tyre and road surface

The control unit detects the wheel speed based on the wheel sensor signals it received, then it calculates the vehicle speed based on the detected wheel speed. The control unit detects the vehicle speed during deceleration based on the rate of deceleration.

The control unit calculates the slip rate of each wheel, and transmits the control signal to the modulator unit solenoid valve when the slip rate is high.

The hydraulic control has three modes: Pressure intensifying, pressure reducing and pressure retaining.

EBD Features

The electronic brake distribution (EBD) helps control vehicle braking by adjusting the rear brake force in accordance with rear wheel load before the ABS operates. Based on wheel sensor signals, the control unit uses the modulator to control the rear brakes individually. When the rear wheel speed is less than the front wheel speed, the ABS modulator-control unit retains the current rear brake fluid pressure by closing the inlet valve in the modulator. As the rear wheel speed increases and approaches the front wheel speed, the ABS modulator-control unit increases the rear brake fluid pressure by momentarily opening the inlet valve. This whole process is repeated very rapidly. While this is happening, there is kickback at the brake pedal.

Modulator Unit

The ABS modulator consists of the inlet solenoid valve, outlet solenoid valve, reservoir, pump, pump motor and the damping chamber. The modulator reduces the caliper fluid pressure directly. It is a circulating-type modulator because the brake fluid circulates through the caliper, reservoir, and the master cylinder. The hydraulic control has three modes; pressure intensifying, pressure retaining, and pressure reducing. The hydraulic circuit is an independent four channel type, one channel for each wheel.

Mode Inlet Solenoid
Valve Outlet Solenoid
Valve Brake Fluid
Pressure intensifying mode open closed Master cylinder fluid is pumped out to the caliper.
Pressure retaining mode closed closed Caliper fluid is retained by the inlet valve and outlet valve.
Pressure reducing mode closed open
Caliper fluid flows through the outlet valve to the reservoir.
The reservoir fluid is pumped out by the pump with the motor^*, through the damping chamber, to the master cylinder.

Mode	Inlet Solenoid Valve	Outlet Solenoid Valve	Brake Fluid
Pressure intensifying mode	open	closed	Master cylinder fluid is pumped out to the caliper.
Pressure retaining mode	closed	closed	Caliper fluid is retained by the inlet valve and outlet valve.
Pressure reducing mode	closed	open	Caliper fluid flows through the outlet valve to the reservoir. The reservoir fluid is pumped out by the pump with the motor^*, through the damping chamber, to the master cylinder.

*: The motor will be keep the action until operation of the one anti-lock brake control is finished from the first pressure reducing mode.