Honda Odyssey 2004. Manual — part 322
05
06
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.
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07
ABS Main Control
19-95
RIGHT-REAR
WHEEL SENSOR
LEFT-REAR
WHEEL SENSOR
RIGHT-FRONT
WHEEL SENSOR
LEFT-FRONT
WHEEL SENSOR
Detect
Wheel Speed
Detect
Wheel Speed
Detect
Wheel Speed
Detect
Wheel Speed
Detect
Vehicle Speed
Select Low
Speed Wheel
Detect
Slip Rate
Detect
Slip Rate
Detect
Slip Rate
REAR
RIGHT-FRONT
LEFT-FRONT
Reference
Slip Rate
ABS
Control
ABS
Control
ABS
Control
Drive
Solenoid
Drive
Solenoid
Drive
Solenoid
Drive
Solenoid
RIGHT-REAR
SOLENOID
LEFT-REAR
SOLENOID
RIGHT-FRONT
SOLENOID
LEFT-FRONT
SOLENOID
ABS/TCS CONTROL UNIT
The ABS/TCS control unit detects the wheel speed based on the wheel sensor signal 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 ABS/TCS control unit calculates the slip rate of each wheel, and it transmits the control signal to the modulator
unit solenoid valve when the slip rate is high.
The pressure reduction control has three modes: pressure intensifying, pressure retaining, and pressure reducing.
(cont’d)
03/07/29 09:56:08 61S0X050_190_0095
01
TCS Main Control
19-96
ABS/TCS Components
System Description (cont’d)
THROTTLE
ANGLE SENSOR
Engine speed signal
Shift position signal
RIGHT-REAR
WHEEL SENSOR
LEFT-REAR
WHEEL SENSOR
RIGHT-FRONT
WHEEL SENSOR
LEFT-FRONT
WHEEL SENSOR
Calculate
traction torque
Calculate
vehicle speed
Calculate drive
wheel speed
difference
Detect
wheel speed
Calculate
slip rate
Calculate control
target value
Calculate control
condition signal
Calculate amount
of right-front
wheel control
Calculate drive
wheel speed
average
Calculate
deviation
Detect
wheel speed
Detect
wheel speed
Detect
wheel speed
Calculate amount
of left-front
wheel control
Drive
solenoid
Drive
solenoid
RIGHT-FRONT
SOLENOID
LEFT-FRONT
SOLENOID
To PCM
Calculate
deviation
ABS/TCS CONTROL UNIT
The ABS/TCS control unit controls the TCS based on signal inputs from the throttle position sensor, engine speed
sensor, shift position sensor, and the wheel sensors. In addition, the ABS/TCS control unit sends an engine retard
request signal to the PCM if necessary. The ABS/TCS control unit uses the modulator unit to control the TCS. The
pressure intensifying control has three modes: pressure intensifying, pressure retaining, and pressure reducing.
03/07/29 09:56:09 61S0X050_190_0096
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−
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ABS Self-Diagnosis
ABS Self-diagnosis Table
Diagnostic
Trouble Code
(DTC)
Detection Item
Detection Timing
Fail-safe Mode
Initial
Diagnosis
Regular
Diagnosis
19-97
• The ABS/TCS control unit is equipped with a main CPU and a sub-CPU. Each CPU checks the other for problems.
• The CPUs check the circuit of the system.
• Self-diagnosis can be classified into two categories:
– Initial diagnosis: Done right after the engine starts and until the ABS or TCS indicator goes off
– Regular diagnosis: Done right after the initial diagnosis until the ignition switch is turned OFF
• When a problem is detected by self-diagnosis, the ABS/TCS control unit shifts to fail-safe mode.
11, 13, 15, 17
Wheel sensor (open/short to body ground/short
to power)
A0
12, 14, 16, 18
Wheel sensor (electrical noise/intermittent
interruption)
A0, L0
21
24
Pulser
A0, L0
31
38
Solenoid (short to body ground/short to wire)
S1
41
44
Wheel lock
A0, L0
51
Motor lock
A0, L0
52
Motor stuck OFF
A0, L0
53
Motor stuck ON
A0, L0
54
ABS fail-safe relay
S1
61
Low ignition voltage
B0, B1
62
High ignition voltage
B0
71
Different diameter tire
S1
81
Central Processing Unit (CPU), ROM/RAM
S1, A1
NOTE:
• At the DTCs with ‘‘
’’ mark, there are cases that the ABS/TCS control unit shifts to fail-safe mode A1, L1 when the
ABS/TCS control unit detects more than one DTC and for different wheel.
• If the ABS/TCS control unit detects the DTCs which have different fail-safe mode individually, the ABS/TCS control
unit take priority the large number mode.
(cont’d)
03/07/29 09:56:09 61S0X050_190_0097
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