1995 ACURA TL Service Repair Manual

System Descriptio n
Outline
Role o f Syste m
Th e tractio n contro l i s a variabl e syste m designe d t o enhanc e tractio n durin g acceleratio n an d cornering . I t doe s s o b y
determinin g th e optimu m amoun t o f whee l spi n fo r an y give n drivin g situation , the n suppressin g surplu s engin e powe r
accordingly .
Constructio n an d Functio n
The TC S contro l uni t get s signal s abou t th e vehicle' s speed , direction , an d roa d condition s fro m sensor s a t th e wheel s an d
the steerin g column . Base d o n thes e signals , th e contro l uni t wil l determin e th e optimu m amoun t o f whee l spin . Becaus e
th e syste m is variable , th e contro l uni t ma y determine , dependin g o n th e drivin g conditions , tha t som e whee l spi n i s bene -
ficia l (thu s enhancin g straight-lin e acceleration) , o r tha t n o whee l spi n i s beneficia l (thu s enhancin g cornering) . Fo r an y
give n drivin g situation , th e contro l uni t wil l determin e th e amoun t o f whee l spi n bes t suite d t o th e driver' s need s and , i f
necessary , wil l the n signa l th e TC S contro l valv e actuato r an d Powertrai n Contro l Modul e (PCM ) t o reduc e engin e power .
Th e syste m is automaticall y "ready " wheneve r th e engine is started , bu t ca n b e manuall y cancele d wit h th e TC S switch .
However , onc e activated , th e syste m canno t b e cancele d unti l i t i s onc e agai n i n th e read y state .
SERVIC E CHEC K CONNECTO R (2P )ABS CONTRO L UNI TTCS CONTRO L UNI TUNDER-DAS H RELA Y BO X
POWERTRAI N
CONTRO L MODUL E (PCM )
EC T SENSO R
TC S CONTRO L VALV E
ANGL E SENSO R STEERIN
G ANGL E SENSO R
RIGHT-REA R WHEE L SENSO R
RIGHT-FRON T
WHEE L SENSO R
Components :
• Whee l sensors : Th e TC S "shares " th e whee l sensor s wit h th e ABS . Th e whee l sensor s transmi t whee l spee d signal s t o
th e TC S throug h th e AB S contro l unit .
• Steerin g angl e sensor : Th e steerin g angl e senso r signal s th e TC S contro l uni t abou t th e amoun t o f steerin g angle .
• TC S contro l valv e sensor : Th e TC S contro l valv e senso r signal s th e TC S contro l uni t abou t th e amoun t o f TC S contro l
valv e angle .
• TC S contro l valv e actuator : Th e actuato r get s signal s fro m th e TC S contro l uni t an d close s th e TC S contro l valv e
accordingly .
• TC S contro l unit : Th e TC S contro l uni t detect s th e drivin g conditio n signal s fro m th e sensor s and , i f necessary , signal s
th e Powertrai n Contro l Modul e (PCM) .
LEFT-REA RWHEEL SENSO R
UNDER-HOO D FUSE/RELA Y BO X
LEFT-FRON
T WHEE L SENSO R
TC
S CONTRO L
VALV E ACTUATO R UNDER-DAS
H FUSE/RELA Y BO X
TC
S SWITC H
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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 BlockProCarManuals.com

System Descriptio n
Fail-Safe Functio n
I f th e contro l uni t detect s a n abnormality , i t shut s th e
tractio n contro l syste m of f an d cause s th e TC S indicato r
ligh t t o com e on . Howeve r i f th e abnormalit y i s detecte d
whil e th e TC S is activated , th e contro l uni t firs t estab -
lishe s th e appropriat e whee l spi n velocity , the n shut s
th e syste m down , thu s preventin g excessiv e whee l spin .
Self-Diagnosi s Functio n
I f th e contro l uni t detect s a n abnormality , i t record s a
Diagnosti c Troubl e Cod e (DTC ) whic h ca n b e use d t o
diagnos e th e problem . Th e DT C is show n a t th e TC S
indicato r ligh t whe n th e Servic e Chec k connecto r termi -
nal s ar e connecte d wit h th e SC S servic e connector .
Steerin g Angl e Detectio n
Steerin g angl e i s detecte d b y th e steerin g angl e sensor .
Th e dis c wit h th e slit s o f th e regula r patter n i s provide d
betwee n th e facin g part s o f th e ligh t emittin g par t (LED) ,
an d th e ligh t receivin g par t (phot o transistor) . A s th e dis c
rotates , i t passe s an d shut s of f th e ligh t fro m th e LED .
The ligh t whic h passe d throug h a sli t i s converte d int o
th e electri c curren t b y th e phot o transistor , an d th e wave -
for m o f thi s electri c curren t i s shape d b y th e comparato r
t o outpu t th e dis c rotatio n a s th e rectangula r signal .
Th e analysi s performanc e o f th e syste m is improve d b y
providin g th e fixe d sli t i n fron t o f th e LED , an d thereb y
identifyin g th e brightnes s an d darknes s o f th e ligh t whic h
i s receive d a t th e phot o transisto r clear .
Th e outpu t signa l i s th e 2-phas e outpu t (A-phas e an d B -
phase) , an d th e steerin g whee l turnin g angl e an d th e
turnin g directio n ar e calculate d b y th e TC S contro l unit .
Vehicl e Spee d Detectio n
Whee l rotatio n spee d i s detecte d b y th e whee l sensors ,
locate d a t eac h wheel . Th e signal s ar e sen t t o th e con -
tro l unit , whic h compare s eac h wheel' s spee d an d deter -
mine s whethe r tractio n contro l i s required .
TCS INDICATO R LIGH T
FIXE D SLI T LIGH
T RECEIVIN G PAR T
(PHOT O TRANSISTOR )
LIGH T EMITTIN G PAR T (LED )
SLIT
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Engine Outpu t Contro l
Whe n th e TC S is activated , th e TC S contro l uni t signal s th e TC S contro l valv e actuato r an d PCM . Th e actuato r i s linke d to
th e TC S contro l valv e whic h is normall y returne d to full y ope n positio n b y th e tw o retur n springs .
Althoug h th e throttl e valv e is stil l withi n th e driver' s control , th e engin e outpu t i s relaxe d b y th e TC S contro l valv e an d
PC M to achiev e optimu m traction .
TCS CONTRO L VALV E SENSO R
TCS CONTRO L VALV E
TCS CONTRO L VALV ERETUR N SPRING S
TCS CONTRO L VALV EACTUATO R (D C MOTOR )
DURING NORMA L DRIVING : DURING TC S ACTUATION :
TC S CONTRO L VALV E
TC S CONTRO L VALV E
ACTUATO R (D C MOTOR ) TC
S CONTRO L VALV E
RETUR N SPRING S
TC S ACTUATIO N SIGNA L
FRO M TC S CONTRO L UNI T
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TCS Control Unit Terminal Arrangement

WIRE SIDE OF FEMALE TERMINALS

VB: Battery Voltage
TCS CONTROL UNIT HP CONNECTORProCarManuals.com

TCS CONTROL UNIT 20P CONNECTOR

WIRE SIDE OF FEMALE TERMINALS

VB: Battery VoltageProCarManuals.com

Troubleshooting Precaution s
1. I n an y o f thes e cases , th e TC S indicato r ligh t ma y com e o n o r sta y o n eve n th e TC S syste m is normal .
• Th e coolan t temperatur e is 32° F (0°C ) o r below .
• Th e parkin g brak e is applie d fo r mor e tha n 3 0 second s whil e th e vehicl e is bein g driven .
• Th e tir e pressur e is no t a t th e specifie d pressure .
• Th e whee l senso r signa l i s interrupte d durin g drivin g a t th e spee d o f 6 mp h (1 0 km/h ) o r abov e du e to , fo r example ,
th e vehicl e spinning .
• Th e MA P sensor , coolan t temperatur e sensor , IC M o r th e atmospheri c pressur e senso r syste m o f th e PGM-F I syste m
is faulty .
2. TC S doe s no t functio n whe n th e TC S indicato r ligh t i s ON .
3 . Whe n bot h th e TC S indicato r ligh t an d th e MI L ar e ON , troubleshoo t th e PGM-F I syste m first .
4 . Whe n bot h th e TC S indicato r ligh t an d th e AB S indicato r ligh t ar e ON , troubleshoo t th e AB S first .
5 . Th e DT C 4- 9 (AB S down ) i s memorize d whe n th e AB S contro l uni t canno t outpu t th e whee l spee d signa l du e to , fo r
example , a missin g o r blow n AB S B 2 (1 5 A ) fuse . I f yo u fai l t o eras e th e DT C o f th e TC S afte r troubleshootin g th e ABS ,
th e DT C remain s in th e TC S contro l uni t memory . Therefore , b e sur e to test-driv e th e vehicl e an d chec k th e TC S indica -
to r ligh t befor e startin g th e troubleshootin g th e TCS .
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Diagnostic Troubl e Cod e (DTC )
Diagnosti c Troubl e Cod e (DTC ) Indicatio n
1. Connec t th e SC S servic e connecto r t o th e servic e chec k connecto r unde r th e glov e box .
2. Tur n th e ignitio n switc h O N (II) , bu t d o no t star t th e engine .
3. Recor d th e blinkin g frequenc y o f th e TC S indicato r light . Th e blinkin g frequenc y indicate s th e diagnosti c troubl e cod e
(DTC) .
4. Tur n th e ignitio n switc h off , an d remov e th e SC S servic e connector .
NOTE : Th e Malfunctio n Indicato r Lam p (MIL ) wil l sta y o n afte r th e engin e is starte d i f th e SC S servic e connecto r i s con -
nected .
5 . Perfor m th e DT C erasure .
SCS SERVIC E CONNECTO R07PAZ-001010 0
TCS INDICATO R LIGH T
SERVIC E CHEC KCONNECTO R (2P )
DTC Indicatio n Patter n
Tur n th e ignitio n switc h O N (II) . Th e TC S indicato r ligh t come s o n t o chec k th e bulb . D o no t coun t i t a s a DTC .
Th e TC S contro l uni t ca n memoriz e u p to thre e DTCs .
A ne w DT C is no t memorize d agai n whe n th e TC S contro l uni t ha s alread y memorize d th e sam e DTC .
The TC S contro l uni t indicate s th e DT C repeatedl y a t interval s o f 3. 3 seconds .
I f yo u miscoun t th e blinkin g frequenc y o r i f yo u rechec k th e blinkin g frequency , tur n th e ignitio n switc h OF F the n tur n i t
O N (II ) t o cycl e th e TC S indicato r ligh t again .
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