Acura 3.5 RL Manual page 854

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.