Acura RL (1996-2004 year). Manual — part 531
Construction and Function
TCS Control unit
Driving Control
When the drive wheel speed exceeds the vehicle speed by a given amount, the TCS control unit judges that the drive
wheels are slipping, and it outputs the traction control signal to reduce engine power.
Handling Control
Based on signals about right and left driven wheel rotational speeds, the control unit calculates the vehicle's "yaw" rate
(the turn rate of the vehicle's body). Based on signals from the steering angle sensor, the control unit also calculates the
yaw rate expected by the driver. If the difference between actual and expected yaw rates is substantial — that is, if the
direction of the vehicle's body will exceed the driver's expected line — the control unit signals the TCS control valve actu-
ator and PCM, thus reducing engine power and maintaining the expected line.
Rough Road Control
Based on signals from the wheel sensors, the control unit detects a rough road based on frequency of wheel rotational
vibration. The control unit then signals the TCS control valve actuator and PCM to relax engine power, thus improving
acceleration efficiency.
Grip Control
Based on signals about wheel speed and yaw rate, the control unit determines the efficiency of the grip of the tires on the
road and signals the TCS control valve actuator and PCM to relax engine power if necessary, thus improving grip.
Main Control Block
Main Menu
Table of Contents
System Description
Fail-Safe Function
If the control unit detects an abnormality, it shuts the
traction control system off and causes the TCS indicator
light to come on. However if the abnormality is detected
while the TCS is activated, the control unit first estab-
lishes the appropriate wheel spin velocity, then shuts
the system down, thus preventing excessive wheel spin.
Self-Diagnosis Function
If the control unit detects an abnormality, it records a
Diagnostic Trouble Code (DTC) which can be used to
diagnose the problem. The DTC is shown at the TCS
indicator light when the Service Check connector termi-
nals are connected with the SCS service connector.
Steering Angle Detection
Steering angle is detected by the steering angle sensor.
A disc with a regular pattern of slits is positioned between
the facing parts of a light emitting part (LED), and a light
receiving part (photo transistor). As the disc rotates, it
interrupts the light from the LED. The light which passes
through a slit is converted into the electric current by the
photo transistor, and the waveform of this electric cur-
rent is shaped by the comparator to output the disc rota-
tion as a rectangular signal.
The analysis performance of the system is improved by
providing the fixed slit in front of the LED, and thereby
identifying the brightness and darkness of the light which
is received at the photo transistor.
The output signal is a 2-phase output (A-phase and Bi-
phase), and the steering wheel turning angle and the
turning direction are calculated by the TCS control unit.
Vehicle Speed Detection
Wheel rotation speed is detected by the wheel sensors,
located at each wheel. The signals are sent to the con-
trol unit, which compares each wheel's speed and deter-
mines whether traction control is required.
FIXED SLIT
LIGHT EMITTING PART (LED)
TCS INDICATOR LIGHT
LIGHT RECEIVING PART
(PHOTO TRANSISTOR)
SLIT
Steering wheel is
turned to right.
Main Menu
Table of Contents
Engine Output Control
When the TCS is activated, the TCS control unit signals the TCS control valve actuator and PCM. The actuator is linked to
the TCS control valve which is normally returned to the fully open position by the two return springs. Although the throttle
valve is still within the driver's control, the engine output is relaxed by the TCS control valve and PCM to achieve optimum
traction.
TCS CONTROL VALVE SENSOR
TCS CONTROL VALVE
TCS CONTROL VALVE
RETURN SPRINGS
TCS CONTROL VALVE
ACTUATOR (DC MOTOR)
DURING NORMAL DRIVING:
DURING TCS ACTUATION:
TCS CONTROL VALVE
TCS CONTROL VALVE
ACTUATOR (DC MOTOR)
TCS CONTROL VALVE
RETURN SPRINGS
TCS ACTUATION SIGNAL
FROM TCS CONTROL UNIT
Main Menu
Table of Contents
TCS Control Unit Terminal Arrangement
TCS CONTROL UNIT 14P CONNECTOR
Wire side of female terminals
VB: Battery Voltage
Terminal
number
1
2
3
4
5
6
7
8
9
10
11
12
13
14
Wire
color
WHT/GRN
BLU/GRY
WHT/RED
BRN/BLK
GRY/BLK
RED
GRY/WHT
LT
GRN/RED
GRY
PNK/BLK
WHT/BLK
BLU/WHT
BRN/YEL
RED/BLK
Terminal sign
(Terminal name)
FRP
(Front right pulse)
WARN1
(Warning 1)
FLP
(Front left pulse)
LG1
(Logic ground 1)
RRP
(Rear right pulse)
TCV
( traction
control valve)
RLP
(Rear left pulse)
TC-INH
(Traction control
inhibit)
STR-B
(Steering B)
TC-STB
(Traction control
standby)
TC-SW
(Traction control
switch)
VREF
(Voltage
reference)
STR-A
(Steering A)
TPS
(Throttle posi-
tion sensor)
Description
Detects right-front
wheel sensor signal
Drives TCS indicator
light (The indicator light
comes on by the
self-bias)
Detects left-front wheel
sensor signal
Ground for the logic
circuit
Detects right-rear wheel
sensor signal
Detects TCS control
valve sensor signal
Detects left-rear wheel
sensor signal
Fl TCS, TCS opera-
tion permission signal
Detects steering angle
sensor signal B
TCS Fl, TCS opera-
tion start signal
Detects TCS switch
signal
Reference voltage for
the sensors of the
PGM-FI system
Detects steering angle
sensor signal A
Detects throttle position
sensor signal
Voltage
Measurement
terminals
1-GND
2-GND
3-GND
4-GND
5-GND
6-GND
7-GND
8-GND
9-GND
10-GND
11-GND
12-GND
13-GND
14-GND
Conditions
(Ignition Switch ON (ID)
Rotate the right-front
wheel.
Indicator light ON
Indicator light OFF
Rotate the left-front
wheel.
Rotate the right-rear
wheel.
TCS control valve is
fully closed.
TCS control valve is
fully open.
Rotate the right-rear
wheel.
Permission (normal)
Inhibition (the coolant
temperature is 0°C or
below)
Failure (TCS and/or
PCM is failure)
Rotate the steering
wheel.
TCS is functioning.
TCS is not functioning.
Push the TCS switch.
Release the TCS switch.
Rotate the steering
wheel.
Throttle valve is fully
closed.
Throttle valve is fully
open.
Output
voltage
About 2.5 V
About 2 V
VB
About 2.5 V
Below 0.3 V
About 2.5 V
About 0.5V
About 4.5 V
About 2.5 V
About 2.5V
(5 V. Duty 50)
About 5 V
About 0 V
5 V 0 V
0 V
About 5 V
VB
0 V
About 5 V
5 V 0 V
About 0.5 V
About 4.5 V
Main Menu
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