ACURA NSX 1991 Service Repair Manual
Manufacturer: ACURA, Model Year: 1991, Model line: NSX, Model: ACURA NSX 1991Pages: 1640, PDF Size: 60.48 MB
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These DTC s wil l b e indicate d b y th e blinkin g o f th e Malfunctio n Indicato r Lam p (MIL ) wit h th e SC S servic e connecto r
connected
Troubleshootin g
Diagnostic Troubl e Cod e (DTC ) Char t
11-65
11-6 7
11-6 9
11-7 0
11-71
11-7 2
11-73
11-7 4
11-75
11-7 7
11-78
11-8 0
11-8 1
11-8 5
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11-82
11-83
11-8 4
11-85
11-7 8
11-80
11-81
11-8 5
11-8 2
11-83
11-8 4
11-8 5
11-87
11-87
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Diagnostic Troubl e Cod e (DTC ) Char t
Troubleshootin g
11-87
11-8 7
11-89
11-8 9
11-10 0
11-10 0
11-16 2
11-160
11-16 0
11-16 8
11-10 2
Sectio n 1 4
indicato r ligh t an d th e Malfunctio n Indicato r Lam p (MIL ) ma y com e o n simultaneously .The
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11-103
11-10 3
11-90
11-10 9
11-10 9
11-11 1
11-111
11-11 4
11-11 4
11-114
Sectio n 6
Sectio n 6
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11-9411-9011-96
11-9611-98
11-98
11-100
11-100
11-100 11-100
11-100
11-100
11-170
Diagnosti c Troubl e Cod e (DTC ) Char t
Troubleshootin g
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indicator ligh t an d th e Malfunctio n Indicato r Lam p (MIL ) ma y com e o n simultaneously .The
11-16 3
11-16 5
11-104
11-10 4
11-105
11-10 5
Sectio n 1 9
Sectio n 1 9
Sectio n 1 4
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Troubleshooting
How to Rea d Flowchart s
A flowchar t i s designe d to b e use d fro m star t t o fina l repair . It' s lik e a ma p showin g yo u th e shortes t distance . Bu t beware :
i f yo u g o of f th e "map " anywher e bu t a "stop " symbol , yo u ca n easil y ge t lost .
Describe s th e condition s o r situatio n to star t a troubleshootin g flowchart .
Ask s yo u to d o something ; perfor m a test , se t u p a conditio n etc .
Ask s yo u abou t th e resul t o f a n action , the n send s yo u in th e appropriat e troubleshootin g direction .
Th e en d o f a serie s o f action s an d decisions , describe s a fina l repai r actio n an d sometime s direct s yo u to
a n earlie r par t o f th e flowchar t t o confir m you r repair .
NOTE:
The ter m "Intermitten t Failure " i s use d in thes e charts . I t simpl y mean s a syste m ma y hav e ha d a failure , bu t i t check s
ou t O K a t thi s time . I f th e Malfunctio n Indicato r Lam p (MIL ) o n th e das h doe s no t com e on , chec k fo r poo r connection s
o r loos e wire s a t al l connector s relate d to th e circui t tha t yo u ar e troubleshootin g (se e illustratio n below) .
Mos t o f th e troubleshootin g flowchart s hav e yo u rese t th e Engin e Contro l Modul e (ECM ) an d tr y t o duplicat e th e
Diagnosti c Troubl e Cod e (DTC) . I f th e proble m is intermitten t an d yo u can' t duplicat e th e code , d o no t continu e throug h
th e flowchart . T o d o s o wil l onl y resul t i n confusio n and , possibly , a needlessl y replace d ECM .
"Open " an d "Short " ar e commo n electrica l terms . A n ope n i s a brea k i n a wir e o r a t a connection . A shor t i s a n acci -
denta l connectio n o f a wir e t o groun d o r t o anothe r wire . I n simpl e electronics , thi s usuall y mean s somethin g won' t
wor k a t all . I n comple x electronic s (lik e ECM's) , thi s ca n sometime s mea n somethin g works , bu t no t th e wa y it' s sup -
pose d to .
TIGH T
LOOS E
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PGM-FI System
System Description
PGM-FI System
The PGM-FI system on this model is a sequential multiport fuel injection system.
Fuel Injector Timing and Duration
The ECM contains memories for the basic discharge durations at various engine speeds and manifold pressures. The
basic discharge duration, after being read out from the memory, is further modified by signals sent from various sensors
to obtain the final discharge duration.
Throttle Valve Control
The ECM controls the throttle valve control motor based on accelerator pedal position, TCS control unit and various sig-
nals. The ECM also controls the idle control function, cruise control function, and other functions with the throttle valve
control.
Ignition Timing Control
• The ECM contains memories for basic ignition timing at various engine speeds and manifold pressures. Ignition timing
is also adjusted for engine coolant temperature.
• A knock control system is also used. When detonation is detected by the knock sensor (KS), the ignition timing is
retarded.
Other Control Functions
1. Starting Control
When the engine is started, the ECM provides a rich mixture by increasing fuel injector duration.
2. Fuel Pump Control
• When the ignition switch is initially turned on, the ECM supplies ground to the PGM-FI main relay that supplies
current to the fuel pump for two seconds to pressurize the fuel system.
• When the engine is running, the ECM supplies ground to the PGM-FI main relay that supplies current to the fuel pump.
• When the engine is not running and the ignition is on, the ECM cuts ground to the PGM-FI main relay which cuts
current to the fuel pump.
• Excellent engine performance is achieved through the use of VTEC (Variable Valve Timing and Valve Lift Electronic
Control System), intake air bypass control and discharge volume control of the fuel pump.ProCarManuals.com
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PGM-FI Syste m
System Descriptio n
3. Fue l Cut-of f Contro l
• Durin g deceleratio n wit h th e throttl e valv e closed , curren t t o th e fue l injector s i s cu t of f t o improv e fue l econom y a t
speed s ove r 1,50 0 rpm .
• Fue l cut-of f actio n als o take s plac e whe n engin e spee d exceeds , 8,30 0 rpm , regardles s o f th e positio n o f th e throttl e
valve , t o protec t th e engin e fro m over-revving .
4 . A/ C Compresso r Clutc h Rela y
Whe n th e EC M receive s a deman d fo r coolin g fro m th e ai r conditionin g system , i t delay s th e compresso r fro m bein g
energized , an d enriche s th e mixtur e to assur e smoot h translatio n to th e A/ C mode .
5 . Evaporativ e Emissio n (EVAP ) Purg e Contro l Solenoi d Valv e
Whe n th e engin e coolan t temperatur e is belo w 153° F (67°C) , th e EC M control s th e EVA P purg e contro l solenoi d valv e
whic h cut s vacuu m to th e EVA P purg e contro l caniste r diaphragm .
6 . Intak e Ai r Bypas s (IAB ) Contro l Solenoi d Valv e
Whe n th e engin e spee d is belo w 4,80 0 rpm , th e IA B contro l solenoi d valv e is activate d b y a signa l fro m th e ECM . Intak e
ai r the n flow s throug h th e smalle r chamber , an d hig h torqu e is delivered . T o increas e ai r flo w a t engin e speed s highe r
tha n 4,80 0 rpm , th e solenoi d valv e is deactivate d b y th e ECM , an d th e intak e ai r flow s throug h th e large r chamber .
7 . Exhaus t Ga s Recirculatio n (EGR ) Contro l Solenoi d Valv e
Whe n th e EG R is require d fo r contro l o f oxide s o f nitroge n (NOx ) emissions , th e EC M supplie s groun d t o th e EG R
contro l solenoi d valv e whic h supplie s regulate d vacuu m to th e EG R valve .
EC M Fail-safe/Back-u p Function s
1 . Fail-Saf e Functio n
Whe n a n abnormalit y occur s i n a signa l fro m a sensor , th e EC M ignore s tha t signa l an d assume s a pre-programme d
valv e fo r tha t senso r tha t allow s th e engin e t o continu e t o run .
2 . Back-u p Functio n
Whe n a n abnormalit y occur s i n th e EC M itself , th e fue l injector s ar e controlle d b y a back-u p circui t independen t o f th e
syste m in orde r t o permi t minima l driving .
3 . Self-diagnosi s Functio n [Malfunctio n Indicato r Lam p (MIL) ]
Whe n a n abnormalit y occur s i n a signa l fro m a sensor , th e EC M light s th e MI L an d store s th e diagnosti c troubl e cod e
i n erasabl e memory . Whe n th e ignitio n i s initiall y turne d on , th e EC M supplie s groun d fo r th e MI L fo r tw o second s t o
chec k th e MI L bul b condition .
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Engine Control Module (ECM)
NOTE: If this symptom is intermittent, check for a loose No. 5 BACK-UP LIGHTS, ALTERNATOR,
TURN SIGNALS (15 A) fuse in the under-dash fuse/relay box, a poor connection at ECM terminal
A7, or an intermittent open in the BLU wire between the ECM (A7) and the gauge assembly.
Is the low oil pressure light on?
Try to start the engine.
Does the engine start?
Check for an open in the wire or
bulb:
1. Turn the ignition switch OFF.
2. Connect the ECM connector ter-
minal A7 to body ground with a
jumper wire.
3. Turn the ignition switch ON (II).
Is the MIL on?
Substitute a known-good ECM,
and recheck. If symptom/indica-
tion goes away, replace the origi-
nal
ECM.
— Repair short in the wire
between No. 5 BACK-UP
LIGHTS, ALTERNATOR, TURN
SIGNALS (15 A) fuse and
gauge assembly.
— Replace No. 5 BACK-UP
LIGHTS, ALTERNATOR, TURN
SIGNALS (15 A) fuse.
ECM CONNECTOR A (26P)
Check for an open in the wires
(PG line):
1. Turn the ignition switch ON (II).
2. Measure voltage between
body ground and ECM connec-
tor terminals A12 and A25 indi-
vidually.
WIRE SIDE OF FEMALE TERMINALS
Is there less than 1.0 V?
Repair open in the wire(s)
between ECM and G101 (located
at intake manifold) that had
more than 1.0V.
— Repair open in the wires
between ECM (A7) and gauge
assembly.
— Replace the MIL bulb.
WIRE SIDE OF FEMALE TERMINALS
ECM CONNECTOR A (26P)
Substitute a known-good ECM
and recheck. If symptom/indica-
tion goes away, replace the origi-
nal
ECM.
Turn the ignition switch ON (II).
The Malfunction Indicator Lamp
(MIL) never comes on (even for
two seconds) after ignition is
turned ON (II).ProCarManuals.com