sensor ACURA NSX 1991 Service Service Manual

Wheel Sensor

The wheel sensor is a contactless type, and it detects the rotating speeds of a wheel. It is composed of a permanent

magnet and coil. When the gear pulsers attached to the rotating parts of each wheel (rear wheel: outboard joint of the

driveshaft, front: hub bearing unit) turn, the magnetic flux around the coil in the wheel sensor alternates, generating

voltages with frequency in proportion to wheel rotating speed. These pulses are inputted into the ABS control unit, and

the ABS control unit identifies the wheel speeds.ProCarManuals.com

Anti-lock Brake System (ABS) Description

Features/Construction/Operation (cont'd)

ABS Control Unit

The ABS control unit consists of a main function section, which controls the operation of anti-lock brake system, and

sub-function, which controls the pump motor and "self-diagnosis."

1. Main Function

The main function section of the ABS control unit performs calculations on the basis of the signals from each wheel

sensor and controls the operation of the anti-lock brake system by putting into action the solenoid valves in the

modulator unit for each front and rear brake.

2. Sub-Function

The sub-function section gives driving signals to the pump motor and also gives "self-diagnosis" signals, necessary

for backing up the anti-lock brake system.

Self-Diagnostic Function

Since the anti-lock brake system modulates the braking pressure when a wheel is about to lock, regardless of the driver's

intention, the system operation and the braking power will be impaired if there is a malfunction in the system. To prevent

this possibility, at speeds above 6 mph (10 km/h), the self-diagnosis function monitors the main system functions. When

an abnormality is detected, the ABS indicator light comes on.

There is also a check mode of the self-diagnosis system itself: when the ignition switch is first turned on, the ABS in-

dicator light comes on and stays on for a few seconds after the engine starts, to signify that the self-diagnosis system is

functional.

Fail-Safe Function

If an abnormality is detected, the ABS control unit turns off the fail-safe relays and motor relay. In this condition, the

anti-lock brake system is prevented from functioning, yet the basic brake system continues to operate normally.

The ABS Indicator Light Comes On

1. When the fluid pressure pump runs more than 120 seconds.

2. When the parking brake is applied for more than 30 seconds while the vehicle is being driven.

3. When the rear wheel(s) is (are) locked more than a specified time.

4. When the wheel rotation signal is not transmitted due to faulty wire or sensor.

5. When the operation time of the solenoid valve(s) exceeds a predetermined valve, and the ABS control unit finds an

open in the solenoid circuit.

6. When the output signals from both main functions in the ABS control unit are not transmitted to the solenoid

valve(s).ProCarManuals.com

ALB Checke r
Function Tes t
NOTE :
• Th e AL B checke r i s designe d t o confir m prope r
operatio n of the anti-loc k brak e syste m (ABS ) b y
simulatin g eac h syste m functio n an d operatin g con -
dition . Befor e usin g th e checker , confir m tha t th e
anti-loc k brak e syste m (ABS ) indicato r ligh t i s no t in -
dicatin g som e othe r proble m wit h th e system . Th e
light shoul d g o o n whe n th e ignitio n i s firs t turne d o n
an d the n g o of f an d sta y of f on e secon d afte r th e
engin e i s started .
• Th e checke r shoul d b e use d throug h modes ,
1-5, t o
confir m prope r operatio n of the system , i n an y on e
of th e followin g situations :
Afte r replacin g an y AB S component .
Afte r replacin g o r bleedin g th e syste m flui d ( 0
mod e no t necessary) .
Afte r an y bod y o r suspensio n repai r tha t ma y
hav e affecte d th e sensor s o r thei r wiring .
• Th e procedur e fo r mode s
1-5 ar e o n thi s pag e an d
19-42 , mod e 0 (whee l senso r signal ) i s o n pag e
19-43 .
1. Wit h th e ignitio n switc h off , disconnec t th e 6- P in -
spectio n connecto r fro m th e connecto r cove r
locate d unde r th e glov e bo x an d connec t th e 6- P in -
spectio n connecto r t o th e AL B checker .
07HAJ-SG0010Bsee pag e 19- 2 fo r othe r applicabl e checkers .
NOTE: Plac e th e vehicl e o n leve l ground with th e
wheel s blocked , pu t th e transmissio n i n neutra l fo r
manua l transmissio n models , an d i n fo r
automati c transmissio n models .
2 . Star t th e engin e an d releas e th e parkin g brake .
3 . Operat e th e AL B checke r a s follows :
(1 ) Tur n th e Mod e Selecto r switc h t o "1" .
(2 ) Pus h th e Star t Tes t switch :
— Th e tes t i n progres s ligh t shoul d com e ON .
— In on e o r tw o mor e seconds , al l fou r monito r
light s shoul d com e o n (I f no t th e checke r i s
faulty) .
— Th e AB S indicato r ligh t shoul d no t com e O N (I f i t
come s o n th e checke r harnes s t o th e 6- P con -
necto r connectio n i s faulty) .
NOTE : Whe n tes t i n progres s indicato r ligh t ON ,
don't tur n th e Mod e Selecto r switch .
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Wheel Sensor Signal Confirmation
NOTE: Us e th e AL B checke r (mod e 0 ) t o confir m pro -
pe r whee l senso r operation .
1 . Disconnec t th e 6- P inspectio n connecto r fro m th e
connecto r cove r locate d unde r th e glov e box , an d
connec t th e 6- P inspectio n connecto r t o th e AL B
checker .
07HAJ-SG0010 Bsee pag e 19- 2 fo r othe r applicabl e checkers .
2. Rais e th e ca r s o tha t al l fou r wheel s ar e of f th e
ground , an d suppor t i t o n safet y stand s (se e pag e
1-9 throug h 1-11 ).
3 . Tur n th e ignitio n switc h O N (II) .
4. Tur n th e Mod e Selecto r switc h t o "0" . 5
. Wit h th e transmissio n in neutral , rotat e eac h whee l
briskl y (on e revolutio n pe r second ) b y hand , an d
confir m tha t it s respectiv e monito r ligh t o n th e
checke r blink s a s th e whee l rotates .
NOTE:
• Rotatin g a whee l to o slowl y wil l produc e onl y a
wea k blin k o f it s monito r ligh t tha t ma y b e dif -
ficul t t o see .
• I n brigh t sunlight , th e monito r ligh t ma y b e dif -
ficul t t o see . Perfor m test s i n a shade d area .
• I n som e instances , i t ma y no t b e possibl e to spi n
th e rea r wheel s fas t enoug h t o ge t a monito r in -
dication , i f necessary , star t th e engin e an d slow -
l y accelerat e an d decelerat e th e rea r wheels .
Th e monito r light s shoul d blin k indicatin g a goo d
whee l senso r signal .
I f an y monito r ligh t fail s t o blink , chec k th e suspecte d
senso r an d pulser , it s ai r ga p an d it s wiring/connectors .
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Fail-Safe Relays/Moto r Rela y
Inspectio n
1. Chec k fo r continuit y betwee n terminal s an d
There shoul d b e n o continuity .
2. Connec t a 1 2 V batter y acros s terminal s an d
There shoul d b e continuit y betwee n terminal s
and
Pulsers/Sensor s
Inspection
1. Chec k th e pulse r fo r chippe d o r damage d teeth .
2 . Measur e ai r ga p betwee n th e senso r an d pulse r al l
th e wa y aroun d whil e rotatin g th e driveshaf t b y
hand .
(A) - (B) = Standard: 0.4-1.0 mm
(0.02-0.04 in.)
NOTE: I f th e ga p exceed s 1. 0 m m (0.0 4 in) , th e
probabilit y i s a distorte d knuckl e whic h shoul d b e
replaced .
KNUCKL E
SENSOR
PULSER
ABS Control Unit
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Pulsers/Sensors
Front Senso r Replacemen t
NOTE:
• B e carefu l whe n installin g th e sensor s t o avoi d
twistin g th e wires .
• Afte r senso r replacemen t confir m prope r opera -
tion (se e pag e 19-43 ).
CORROSIO N RESISTAN T BOL T6 x 1. 0 m m10 N- m (1. 0 kg-m . 7 Ib-ft )
6 x 1. 0 m m10 N- m (1. 0 kg-m ,7 Ib-ft )
8 x 1.2 5 mm22 N- m (2. 2 kg-m ,16 Ib-ft )
Rear Senso r Replacemen t
8 x 1.2 5 mm22 N- m (2. 2 kg-m , 1 6 Ib-ft )
NOTE :
• B e carefu l whe n installin g th e sensor s t o avoi d
twistin g th e wires .
• Afte r senso r replacement , confir m prope r opera -
tion (se e pag e 19-43 ).
CORROSIO N RESISTAN T BOL T
6 x 1. 0 m m10 N- m (1. 0 kg-m , 7 Ib-ft )
6 x 1. 0 m m10 N- m (1. 0 kg-m ,7 Ib-ft )
6 x 1 0 m m10 N- m (1. 0 kg-m ,7 Ib-ft )
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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
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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) .
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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
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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
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