Yamaha Tracer MT09TRA - Service manual > Abs component functions

Wheel sensors and wheel sensor rotors

Wheel sensors "1" detect the wheel speed and transmit the rotation signal to the ABS ECU.

Each wheel sensor is composed of a permanent magnet and a hall IC. The sensor rotors "2" rotate with the wheels. The sensor rotors "2" have 40 slots and are installed close to the wheel sensors. As the sensor rotor rotates, the hall element in the hall IC installed in the wheel sensor generates pulses. The pulse frequency, which is proportional to the magnetic flux density, is converted into a wave in the hall IC so that it can be output.

The ABS ECU calculates the wheel rotation speed by detecting the pulse frequency.

3. At low speed
4. At high speed
5. Wheel sensor
6. Wheel sensor rotor
7. Voltage
8. Time

ABS warning light

The ABS warning light "1" comes on to warn the rider if a malfunction in the ABS occurs.

When the main switch is turned to "ON", the ABS warning light comes on to check the electrical circuit and the system function (ABS self-diagnosis), and goes off when the vehicle is operated (the function check is properly completed at a speed of about 6 to 10 km/h [3.8 to 6.3 mi/h]).

TIP

After all checks and servicing are completed, the ABS warning light will go off when the vehicle is ridden or pushed at a speed of 7 km/h (4 mi/h) or faster.

NOTICE

If the rear wheel is raced with the vehicle on the centerstand, the ABS warning light may flash or come on. If this occurs, turn the main switch to "OFF", then back to "ON". The ABS operation is normal if the ABS warning light goes off after the vehicle starts off. If the fault codes are not deleted, the ABS warning light goes off after the vehicle is ridden at a speed of approximately 30 km/h (19 mph).

Hydraulic unit assembly

The hydraulic unit assembly "1" is composed of hydraulic control valves (each with a outlet solenoid valve and inlet solenoid valve), buffer chambers, hydraulic pumps, an ABS motor, and ABS ECU. The hydraulic unit adjusts the front and rear wheel brake fluid pressure to control the wheel speed according to signals transmitted from the ABS ECU.

Hydraulic control valve

The hydraulic control valve is composed of a inlet solenoid valve and outlet solenoid valve.

The electromagnetic force generated in the inlet solenoid valve varies proportionally with the duty cycle control voltage that is supplied to it. Since this voltage is continuously variable, the solenoid valve moves smoothly and the hydraulic pressure is adjusted linearly.

1. When the brakes are operated normally, the inlet solenoid valve "1" is open and the outlet solenoid valve "2" is closed. The brake line between the brake master cylinder and brake caliper is open.

2. When the ABS is activated, the inlet solenoid valve "1" closes and the outlet solenoid valve "2" opens using the power supplied from the ABS ECU signals. This reduces the hydraulic pressure.

3. When the ABS ECU sends a signal to stop reducing the hydraulic pressure, the outlet solenoid valve "2" closes and the brake fluid is pressurized again. The inlet solenoid valve "1" controls the hydraulic pressure difference between the brake fluid in the upper brake lines (brake master cylinder side) and the brake fluid in the lower brake lines (brake caliper side).

Buffer chamber

The buffer chamber accumulates the brake fluid that is depressurized while the ABS is operating.

1. Buffer chamber (pressurizing phase)
2. Buffer chamber (depressurizing phase)
3. Raised piston

ABS ECU

The ABS ECU is integrated with the hydraulic unit to achieve a compact and lightweight design.

As shown in the following block diagram, the ABS ECU receives wheel sensor signals from the front and rear wheels and also receives signals from other monitor circuits.

1. Battery
2.  AC magneto
3.  Rectifier/regulator
4.  Main fuse
5.  ABS motor fuse
6.  ABS solenoid fuse
7.  Main switch
8.  ABS ECU fuse
9.  Signaling system fuse
10. Rear brake light switch
11. Front brake light switch
12. Tail/brake light
13. ABS test coupler
14. Hydraulic unit assembly
15. ABS ECU
16. ABS motor relay
17. Solenoid relay
18. Front brake outlet solenoid
19. Front brake inlet solenoid
20. Rear brake outlet solenoid
21. Rear brake inlet solenoid
22. ABS motor
23. Meter assembly
24. ABS warning light
25. ECU (engine control unit)
26. Front wheel sensor
27. Rear wheel sensor

The necessary actions are confirmed using the monitor circuit and control signals are transmitted to the hydraulic unit assembly.

ABS control operation

The ABS control operation performed in the ABS ECU is divided into the following two parts.

• Hydraulic control
• Self-diagnosis

When a malfunction is detected in the ABS, a fault code is stored in the memory of the ABS ECU for easy problem identification and troubleshooting.

TIP

• Some types of malfunctions are not recorded in the memory of the ABS ECU (e.g., a blown ABS ECU fuse).
• The ABS performs a self-diagnosis test for a few seconds each time the vehicle first starts off after the main switch was turned on. During this test, a "clicking" noise can be heard from under the seat, and if the brake lever or brake pedal are even slightly applied, a vibration can be felt at the lever and pedal, but these do not indicate a malfunction.

1. Software operation flow
2.  Main switch "ON"
3.  Initialize
4.  Self-diagnosis (when static)
5. Self-diagnosis (when riding)
6.  Receive signals
7.  Control operation
8.  Depressurize/pressurize

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