Honda 2004 Odyssey, Service Manual

Page: 1295 / 2459

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ABS Features
Grip Force of Tire and Road Surface
TCS Features
Electronic Brake Distribution (EBD) Features
19-94
ABS/TCS Components
System Description (cont’d)
COEFFICIENT OF
FRICTION
TARGET SLIP RATE
ROTATIONAL
DIRECTION
RADIAL
DIRECTION
OF THE
ROTATIONAL
DIRECTION
SLIP RATE
NORMAL ROAD SURFACE
SLIPPERY ROAD SURFACE
When the brake pedal is pressed while driving, the wheels can 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. The ABS precisely controls the slip
rate of the wheels to ensure maximum grip force from the tires, and it thereby ensures maneuverability and stability
of the vehicle.
The ABS calculates the slip rate of the wheels based on the vehicle speed and the wheel speed, then it controls the
brake fluid pressure to reach the target slip rate.
The TCS provides low-speed traction. When a drive wheel loses traction on a slipperly road surface and starts to spin,
the ABS/TCS control unit sends a brake signal to the modulator unit, which applies brake pressure to slow the
spinning wheel. At that time, the ABS/TCS control unit sends an engine retard signal to the PCM to prevent damage to
the transmission.
The electronic brake distribution (EBD) function helps control vehicle braking by adjusting the rear brake force before
the ABS operates, based on wheel sensor signals, the ABS 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 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 control unit increases the rear brake fluid pressure by momentarily opening the
inlet valve. This whole process is repeated very rapidly.
03/07/29 09:56:08 61S0X050_190_0094