engine ACURA NSX 1991 Service Owners Manual

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

Diagnostic Trouble Code (DTC):

1. Stop the engine.

2. Disconnect the service check connector from the connector cover located under the glove box.

Connect the two terminals of the service check connector with a jumper wire.

3. Turn the ignition switch on, but do not start the engine.

4. Record the blinking frequency of the ABS indicator light.

The blinking frequency indicates the diagnostic trouble code (DTC).

CAUTION: Before starting the engine, disconnect the jumper wire from the service check connector, or else the

Malfunction Indicator Lamp (MIL) will stay on with the engine running.

NOTE:

• The ABS control unit can indicate three DTCs (one, two or three problems).

• If the ABS indicator light does not light, see Troubleshooting of ABS Indicator Light Circuit page 19-44.

• If you miscount the blinking frequency, turn the ignition switch off, then turn on to blink the ABS indicator light

again.

• After the repair is completed, disconnect the ABS 2,3 (20A) fuse for at least three seconds to erase the ABS

control unit's memory. Then turn the ignition key on again and recheck.

• The memory is erased if the connector is disconnected from the ABS control unit or the ABS control unit is re-

moved from the body.

• After recording the main and sub-code (if applicable), refer to the Symptom-to-System Chart.ProCarManuals.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
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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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Troubleshooting
TCS Indicato r Ligh t
Temporar y Drivin g Conditions :
1 . Th e TC S indicato r ligh t wil l com e o n an d th e contro l uni t memorize s th e Diagnosti c Troubl e Cod e (DTC ) unde r certai n
temporar y conditions :
• Th e spar e tir e is installed , o r a tir e o f th e imprope r siz e is installed .
• Th e tir e pressure s ar e no t correct .
2 . I f th e TC S indicato r ligh t doe s no t com e bac k o n afte r correctin g th e tir e o r tir e pressur e problem , th e TC S syste m is
OK .
3. Remov e th e CLOC K (7. 5 A ) fus e fo r a t leas t thre e second s to clea r th e DT C fro m th e TC S contro l uni t memory .
NOTE : Disconnectin g th e CLOC K fus e als o cancel s th e radi o prese t station s an d th e cloc k setting . Mak e not e o f th e
radi o preset s befor e removin g th e fus e s o yo u ca n rese t them .
TC S Diagnosti c Troubl e Cod e (DTC ) Indication :
1 . Sto p th e engine .
2 . Tur n th e ignitio n switc h O N (II) , an d confir m tha t th e TC S indicato r ligh t come s on .
3 . Tur n th e ignitio n switc h off .
4 . Connec t th e SC S servic e connecto r t o th e servic e chec k connecto r locate d unde r th e glov e box .
5 . Tur n th e ignitio n switc h O N (II) , bu t d o no t star t th e engine .
6 . 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 DTC . Lon g blink s indi -
cat e th e mai n code : shor t blink s indicat e th e sub-code .
7 . Refe r t o th e Troubleshootin g Guid e (pag e 19-88 ) fo r repai r information .
SERVICE CHEC KCONNECTO R (2P )
TCS INDICATO R LIGH T
SCS SERVIC E CONNECTO R07PAZ-001010 0
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Steering angle sensor system check

1. Start the engine,
2. Push the TCS switch three times within three seconds.
NOTE: Always maintain the same number of rota-
tions.
3. Turn the steering wheel slowly from left to right more than 1.5 turns.

NOTE:
Start checking after the steering wheel moves at
least 1.5 turns from right to left.
Turn the steering wheel slowly, no faster than
one turn in four seconds.
4. Push the TCS switch twice within three seconds. NOTE: Always maintain the same number of rota-
tions.
5. Return the steering wheel to the left side slowly, and check the number of times the TCS indicator light
flashes after the wheel has moved approximately
one turn.

NOTE:

Start the check from the beginning when the steer-ing wheel moves at least one turn from left to
right, Turn the steering wheel slowly, no faster than one
turn in four seconds.
Standard number of times the TCS indicator light

flashes:
Manual Transmission: 5 times
Automatic Transmission: 2 times
6. If there is an abnormality, check the troubleshooting flowchart (see page 19-98('91-'93)('94-'96)
Selection of the adjusting shims for the steering angle

sensor air gap adjustment

NOTE:

The adjustment of the air gap between the steeringshaft and the steering angle sensor should be carried
out in order to obtain adequate sensor output.
The adjusting shim reference number is stamped on
the steering column. Select the adjusting shims that match the reference number using the table below.
Reference Number Locations

REFERENCE

NUMBER

STEERING

COLUMN
Selection of The Adjusting Shim
Adjusting Shim Parts Number

A:53395–SL0–A01
B: 53396–SL0–A01

C: 53397–SL0–A01
D: 53398–SL0–A01
Thickness

0.1 mm

0.2 mm

0.4 mm

0.7 mm
Color

Yellow
Black

Green

White

Reference Number

1

2

3

4

5

6

7

8
Shim (P/N): (Thickness)
Not used: (0 mm)

A:
(0,1
mm)
B:
(0.2
mm)

A + B:
(0.3
mm)
C:
(0.4
mm)

A + C:
(0.5
mm)

B + C:
(0.6
mm)
D:
(0.7
mm)ProCarManuals.com

Rear Hatch/Engin e Cove r
Replacement/Adjustmen t
CAUTION: Us e fende r cover s t o avoi d damagin g painte d surfaces .
1 . Remov e th e engin e cover .
2 . Remov e th e connecto r cover , an d disconnec t th e rea r defogger , antenn a lea d an d groun d cabl e connectors .
3 . Remov e th e rea r hatc h assembl y b y removin g th e suppor t stru t mountin g bolt s an d rea r hatc h mountin g bolts .
NOTE :
• Hav e a n assistan t hol d th e rea r hatc h assembl y whe n removin g th e suppor t struts .
• Tak e car e no t t o damag e th e roo f pane l an d rea r hatc h glass .
4 . Installatio n i s th e revers e o f th e remova l procedure .
NOTE :
• Befor e tightenin g th e mountin g bolts , adjus t th e rea r hatc h assembl y an d striker .
• Wit h th e rea r hatc h assembl y close d fully , chec k fo r wate r leaks .
ROD HOLDE RTurn th e holde r 45 ° t oremov e it .
6 x 1. 0 m m10 N m (1. 0 kg-m ,7.2 Ib-ft )
GROUN D CABL ECONNECTO R
ANTENNA LEA DCONNECTO R
STRIKER ADJUSTMEN TAdjust th e rea r hatc h assembl yfit t o th e hatc h openin gby movin g th e striker .
REAR DEFOGGE RCONNECTO R
SUPPORT STRU TMOUNTIN G BOL T8 x 1.2 5 mm22 N- m (2. 2 kg-m ,16 Ib-ft )
6 x 1. 0 m m10 N- m (1. 0 kg-m ,7.2 Ib-ft )
SUPPOR TSTRUT
CORROSIO N RESISTAN T BOL T
SUPPOR T STRU TMOUNTIN G BOL T6 x 1. 0 m m10 N- m (1. 0 kg-m ,7.2 Ib-ft )
CONNECTO RCOVER
ENGIN E COVE REDGE CUSHIO NTurn a s neede d t omak e th e engin e cove r fi tflus h wit h th e body .
HINGE MOUNTIN G NU T8 x 1.2 5 mm22 N- m (2. 2 kg-m , 1 6 Ib-ft )
HING E
REAR HATC HASSEMBL Y
ENGINECOVER
FENDE RCOVER
REAR HATC HMOUNTIN G BOLT S6 x 1. 0 m m10 N- m (1. 0 kg-m ,7.2 Ib-ft )
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Engine Cover/Roo f Cove r
Remova l
NOTE:
• Tak e car e no t t o scratc h th e body .
• Ope n th e rea r hatch .
1 . Ope n th e engin e cover , an d suppor t i t wit h th e sup -
por t rod . Disconnec t th e roo f holde r switc h connec -
tor , remov e th e nut , the n remov e th e groun d wire .
NOTE : I f necessary , remov e th e roo f switc h sub -
harness .
ENGINE COVE R
CONNECTO R
CONNECTO R GROUN DWIRE
ROO F HOLDE R SWITC HSUB-HARNES S
2. Remov e th e suppor t ro d fro m th e engin e cover .
Remov e th e bolts , tha n remov e th e engin e cover .
ENGIN E COVE R
ENGIN E COVE R
EDGE CUSHION S
ENGINE COVE RHINGE
BOLT S6 x 1. 0 m m10 N- m (1. 0 kg-m ,7.2 Ib-ft )
CORROSIO N RESISTAN T BOL T
3. Installatio n i s th e revers e o f th e remova l procedure .
NOTE:
• Mak e sur e th e roo f holde r switc h connecto r i s
connecte d properly .
• I f necessary , tur n th e engin e cove r edg e cush -
ion s t o mak e th e engine cover fi t flus h wit h th e
body .
SUPPOR TROD
ENGINE COVER
EDGE CUSHIONS
GROMME T
ROOF HOLDE RSWITCH
HARNES SCLIPNUT
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Engine Cover/Roo f Cove r
Replacemen t
NOTE:
• Tak e car e no t t o scratc h th e body .
• Ope n th e rea r hatch .
Roof cove r (Engin e cover ) removal :
1. Ope n th e roo f cover , remov e th e nuts , the n remov e
th e roo f cover .
Nut locations , 4
6 x 1. 0 m m10 N- m (1. 0 kg-m ,7.2 Ib-ft )STRIKE R
ROOF COVE RLATCH
NOTE : Afte r installin g th e roo f cover , adjus t th e
roo f cove r latc h b y usin g shim s t o mak e th e roo f
cove r loc k securel y (se e pag e 20-113 ).
2 . I f removin g th e engin e cover , remov e th e groun d
wire , disconnec t th e roo f holde r switc h connector ,
the n detac h th e harnes s cli p fro m th e lef t sid e (se e
pag e 20-111 ). Remov e th e nuts , the n remov e th e
engin e cover .
Nut locations , 4
ENGIN E COVE R
ENGINECOVERHINGE
NUTS6 x 1. 0 m m 10 N- m(1.0 kg-m , 7. 2 Ib-ft )
3. Installatio n is th e revers e o f th e remova l procedure .
NOTE : Mak e sur e th e roo f cove r open s properl y an d
lock s securely .
ROOF COVE R
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