1991 ACURA NSX Service Repair Manual

Special Tools

Ref.
No.

Tool Number

07PAZ-0010100
Description

SCS Service Connector
Qty

1

19-84('91-'93)('94-'96)Page ReferenceProCarManuals.com

Component Location s
ENGINE CONTRO L MODUL E (ECM )
ABS CONTRO L UNI T
UNDER-HOO D
FUSE/RELA Y BO X
RIGHT-FRON T
WHEE L SENSO R RIGHT-REA
R WHEE L SENSO R
TRANSMISSIO N CONTRO L MODUL E (TCM )
THROTTL E BOD Y
THROTTL E ACTUATO R
LEFT-REARWHEEL SENSO R
TC S SWITC H
LEFT-FRON T
WHEE L SENSO R
TCS CONTRO L UNI T
LATERAL ACCELERATION (Lg) SENSOR
A/T GEA R POSITIO N SWITC H
UNDER-DAS H FUS E BO X
GAUG E ASSEMBL Y UNDER-HOO
D FUSE/RELA Y BO X
BRAK E LIGHTS/HOR N (2 0 A ) FUS E
TC S INDICATO R LIGH T
I G S W (A ) (5 0 A ) FUS E
UNDER-DAS H FUS E BO X CLOC
K (7. 5 A ) FUS E
BACK-U P LIGHTS/ALTERNATOR /
TUR N SIGNAL S (1 5 A ) FUS E
STEERIN
G ANGL E SENSO R
ProCarManuals.com

System Descriptio n
Outline
Role o f Syste m
Th e NSX/NSX- T 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 .
Thi s versio n o f TC S ha s a latera l acceleratio n (Lg ) senso r an d a deceleratio n contro l functio n t o improv e tractio n contro l
durin g acceleratio n an d deceleratio n whil e cornering . Whe n downshiftin g quickl y t o a ver y lo w gea r o n a slipper y surface ,
th e drivin g wheel s ten d t o sli p becaus e o f engin e braking , resultin g i n lowe r directiona l stability . T o counterac t this , th e
deceleratio n contro l functio n control s engine braking wit h th e TC S contro l unit .
Constructio n an d Functio n
Th e 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
th e 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 throttl e actuato r an d Engin e Contro l Modul e (ECM ) t o reduc e engin e power .
Th e syste m is automaticall y "ready " wheneve r th e engin e i s 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 in th e read y state .
ENGIN E CONTRO L MODUL E (ECM )
STEERIN G ANGL E SENSO R
TC S SWITC H RIGHT-REA
R WHEE L SENSO R
THROTTL E BOD Y
ABS CONTRO L UNI T
RIGHT-FRON T
WHEE L SENSO R THROTTL
E ACTUATO R
LEFT-REARWHEEL SENSO R
LEFT-FRON T
WHEE L SENSO R TC
S CONTRO L UNI T
LATERAL ACCELERATION (Lg) SENSOR
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 .
• Latera l acceleratio n (Lg ) sensor : Th e L g senso r detect s th e latera l acceleratio n o f th e vehicl e an d signal s th e TC S con -
trol unit .
• 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 throttl e actuato r an d th e Engin e Contro l Modul e (ECM) . Thi s versio n ha s a latera l acceleratio n (Lg ) sensor , whic h
improve s th e tractio n contro l performanc e durin g cornering .
• Throttl e actuator : Th e throttl e actuato r open s an d close s th e throttl e valv e accordin g to th e tractio n contro l signa l fro m
the Engin e Contro l Modul e (ECM) .
ProCarManuals.com

Construction an d Functio n
TCS Contro l uni t
Acceleratio n Contro l
Whe n th e driv e whee l spee d exceed s th e vehicl e spee d b y a give n amount , th e TC S contro l uni t judge s tha t th e driv e
wheel s ar e slipping , an d it output s th e tractio n contro l signa l t o reduc e engin e power .
Deceleratio n Contro l
Whe n th e driv e whee l spee d drop s belo w th e vehicl e spee d b y a give n amount , th e TC S contro l uni t judge s tha t th e driv e
wheel s ar e slipping , an d it output s th e tractio n contro l signa l t o contro l engin e brakin g properly .
Handlin g Contro l
Base d o n signal s abou t drivin g whee l an d drive n whee l rotationa l speeds , th e contro l uni t calculate s th e car' s "yaw" rate
(th e tur n rat e o f th e car' s body) . Base d o n signal s fro m th e steerin g angl e sensor , th e contro l uni t als o calculate s th e ya w
rat e expecte d b y th e driver . I f th e differenc e betwee n actua l an d expecte d ya w rate s is substantia l — tha t is , i f th e directio n
of th e car' s bod y will excee d the driver' s expecte d lin e — the contro l unit signal s the throttl e actuator , whic h close s the
throttl e valve , thu s reducin g engin e powe r an d maintainin g th e expecte d line .
Roug h Roa d Contro l
Base d o n signal s fro m th e whee l sensors , th e contro l uni t detect s a roug h roa d base d o n frequenc y o f whee l rotationa l
vibration . Th e contro l uni t the n signal s th e throttl e actuato r t o rela x engine power, thu s improvin g acceleratio n efficiency .
Gri p Contro l
Base d o n signal s abou t whee l spee d an d latera l acceleration , th e contro l uni t determine s th e efficienc y o f th e gri p o f th e
tire s o n th e roa d an d signal s th e throttl e actuato r t o rela x engine power i f necessary , thu s improvin g grip .
Mai n Contro l Bloc k
ProCarManuals.com

System Descriptio n
Constructio n an d Functio 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 i s 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 is detecte d b y th e steerin g angl e sensor ,
locate d o n th e steerin g column . Th e senso r use s tw o
magneto-resisto r (MR ) element s t o determin e steerin g
angl e an d directio n o f rotation . Whe n th e drive r turn s
th e steerin g wheel , a magne t i n th e steerin g shaf t gener -
ate s wave s i n th e "MR " elements . Thes e wave s ar e
amplifie d an d converte d int o signal s whic h th e contro l
uni t ca n interpre t a s angl e an d directio n o f turn .
MR ELEMEN T
TCS INDICATO R LIGH T
MRELEMEN T
Vehicle 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 .
GEAR PULSE R
WHEEL SENSO R
ProCarManuals.com

Lateral Acceleration Detection

Lateral acceleration is detected by the lateral accelera-

tion (Lg) sensor located under the rear center trim panel.

The Lg sensor varies the output voltage in accordance

with the left or right side acceleration and sends it to the

TCS control unit as a lateral acceleration signal.
Lg SENSOR

90 degrees

VOLTAGE
RIGHT SIDE ACCELERATION

OUTPUT CHARACTERISTIC

LEFT

TURN
RIGHT

TURN
LATERAL

ACCELERATIONProCarManuals.com

TCS Contro l Uni t Termina l Arrangemen t
ProCarManuals.com

ProCarManuals.com