fuse ACURA NSX 1991 Service Repair Manual

Engine Removal/Installation

Removal

20. Disconnect the engine wire harness connectors.

21. Remove the battery cable from the main fuse box.

ENGINE WIRE

HARNESS CONNECTORS

BATTERY

CABLE

6 x 1.0 mm

10 N-m
(1.0 kg-m,

7 Ib-ft)

22. Disconnect the throttle body 6P connector, and

remove the ground cable and starter cable.

STARTER CABLE
THROTTLE BODY

6P CONNECTOR

GROUND CABLE

CORROSION RESISTANT BOLT
23. Disconnect the two connectors from the emission

control box, then remove the control box.

• Do not disconnect the vacuum hoses.

6 x 1.0 mm

10 N-m (1.0 kg-m, 7 Ib-ft)

CONNECTORS

CONTROL BOX

24. Remove the radiator hoses and heater hose.

HEATER HOSE

RADIATOR

HOSESProCarManuals.com

II. Engine Control Module (ECM) Reset Procedure

Either of the following actions, will reset the ECM.

• Using the OBD-II scan tool or Honda PGM Tester to clear the ECM's memory.

NOTE: See the OBD-II scan tool or Honda PGM Tester user's manuals for specific operating instructions.

• Turn the ignition switch OFF. Remove the CLOCK (7.5 A) fuse from the under-hood fuse/relay box for 10 seconds.

UNDER-HOOD

FUSE/RELAY BOX
CLOCK

(7.5 A) FUSE

III. Final Procedure (this procedure must be done after any troubleshooting)

1. Remove the SCS Service Connector if it is connected.

NOTE: If the SCS service connector is connected and there are no DTCs stored in the ECM, the MIL will stay on

when the ignition switch is turned on.

2. Do the ECM Reset Procedure.

3. Turn the ignition switch OFF.

4. Disconnect the OBD-II scan tool or Honda PGM Tester from the Data Link Connector,ProCarManuals.com

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

PGM-FI Syste m
Engine Contro l Modul e (ECM )
The Malfunctio n Indicato r Lam p
(MIL ) stay s o n o r come s o n afte r
tw o seconds .
Check th e Diagnosti c Troubl eCode (DTC) :
1 . Connec t a sca n too l o r Hond a
PG M Tester .
2 . Tur n th e ignitio n switc h O N (II) .
3 . Rea d th e DT C wit h th e sca n
too l o r Hond a PG M Tester .
NOTE:• Whe n ther e is n o Diagnosti c Troubl e Cod e (DTC ) stored , th e MI L wil l sta y o n i f th e SC S servic e
connecto r i s connecte d an d th e ignitio n switc h i s on .
• I f thi s sympto m is intermittent , chec k for :
— A loos e ACG(S ) (20 A ) fus e in th e engin e compartment fuse/rela y box— A loos e No . 2 FUE L PUM P SRS 2 (1 5 A ) fus e in th e under-das h fus e bo x
— A n intermitten t shor t i n th e wir e betwee n th e EC M (C5 ) an d th e servic e chec k connecto r
— A n intermitten t ope n i n th e wire s betwee n th e EC M (A26 , B14 ) an d th e servic e chec k con -
necto r
— A n intermitten t shor t i n th e wir e betwee n th e EC M (A7 ) an d th e gaug e assembl y— A n intermitten t shor t i n th e wir e betwee n th e EC M (F1 ) an d th e MA P sensor , accelerato r posi -
tio n senso r
— A n intermitten t shor t i n th e wir e betwee n th e EC M (D10 ) an d th e T P sensor , EG R valv e lif t
senso r— A n intermitten t shor t i n th e wir e betwee n th e EC M (F14 ) an d accelerato r positio n senso r
• Se e th e OBD-I I sca n too l o r Hond a PG M Teste r user' s manual s fo r specifi c operatin g instruc -
tions .
Ar e an y DTC(s ) indicated ? G
o to troubleshootin g procedures .
(se e pag e 11-38 )
Chec k th e DT C b y MI L indication :
1 . Tur n th e ignitio n switc h OFF .
2 . Connec t th e SC S servic e con -
necto r t o th e servic e chec k
connector .
3 . Tur n th e ignitio n switc h O N (II) .
Doe s th e MI L indicat e an y DTC ? Repai
r ope n o r shor t i n wir e
betwee n th e EC M (D4 ) an d
Dat a Lin k Connector .
G o t o troubleshootin g proce -
dures . (se e pag e 11-38 )
Tr y t o star t th e engine .
Doe s th e engin e start ?
Chec k fo r a shor t i n th e wire s
(SC S line) :
1. Sto p th e engin e an d tur n th eignitio n switc h O N (II) .2. Measur e voltag e betwee n th e
EC M connecto r termina l C 5
an d bod y ground . (T
o pag e 11-63 )
I s ther e approx . 5 V ?
(T o pag e 11-63 ) Repai
r shor t t o bod y groun d i n
th e wir e betwee n EC M (C5 ) an d
servic e chec k connector .
ProCarManuals.com

(From pag e 11-62 )
Chec k fo r a shor t i n th e wire s
(MI L line) :
1. Tur n th e ignitio n switc h OFF .2. Disconnec t th e EC M connec -tor A (26P) .3. Tur n th e ignitio n switc h O N (II) .
Is th e MI L ON ?Repai r shor t t o bod y groun d i n
th e wir e betwee n th e EC M (A7 )
and MIL .
Substitut e a known-goo d EC M
an d recheck . I f symptom/indica -
tio n goe s away , replac e th e origi -
nal ECM .
(From pag e 11-62 )
Inspec t ACG(S ) (2 0 A ) fus e i n th e
engin e compartmen t fuse/rela y
box.
Is th e fus e OK ? Repai
r shor t i n th e wir e
betwee n ACG(S ) (2 0 A ) fus e
an d PGM-F I mai n relay .
Replac e ACG(S ) (2 0 A ) fuse .
Inspec t I G COI L (3 0 A ) fus e i n th e
engin e compartmen t fuse/rela y
box.
Is th e fus e OK ? Repai
r shor t i n th e wir e
betwee n I G COI L (3 0 A ) fus e
an d PGM-F I mai n relay .
Replac e IG COI L (3 0 A ) fuse .
Chec k fo r a shor t i n a sensor :
1. Tur n th e ignitio n switc h O N (II) .2. Disconnec t th e 3 P connecto r
o f eac h senso r on e a t time :
• MA P senso r
• T P senso r
• EG R valv e lif t senso r
Doe s th e MI L remai n ON ? Replac
e th e senso r tha t cause d
the ligh t t o g o out .
(To pag e 11-64 )
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Idle Contro l Syste m
Brake Switc h Signa l
This signal s th e EC M whe n th e brak e peda l i s depressed .
Are th e brak e light s o n withou tdepressin g th e brak e pedal ?Inspec t th e brak e switc h (se e
sectio n 19 ).
Depres s th e brak e pedal .
D o th e brak e light s com e on ?
Is th e fus e OK ?
Chec k fo r a n ope n in th e wire :
1 . Depres s th e brak e pedal .
2 . Measur e voltag e betwee n
EC M connecto r terminal s F1 6
an d A2 6 wit h th e brak e peda l
depressed . —
Repai r shor t i n th e wir e
betwee n th e brak e switc h
an d th e BRAK E LIGH T S W
HOR N (2 0 A ) fuse .
— Replac e th e BRAK E LIGH T
S W HOR N (2 0 A ) fuse .
WIR E SID E O F FEMAL E TERMINAL S
I s ther e batter y voltage ? Repai
r ope n i n th e wir e betwee n
th e EC M (F16 ) an d th e brak e
switch .
Inspectio
n o f Brak e Switc h Signal .
Inspect th e BRAK E LIGH T S W
HORN (20 A ) fus e i n th e under -
hood fuse/rela y box .
Repai r ope n i n th e wir e
betwee n th e brak e switc h
an d th e BRAK E LIGH T S W
HOR N (2 0 A ) fuse .
Inspec t th e brak e switc h (se e
sectio n 19 ).
ECM CONNECTOR S
Brak e switc h signa l i s OK .
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Starter Switch Signal

This signals the ECM when the engine is cranking.

Inspection of Starter Switch Sig-

nal.
NOTE:

• M/T: Clutch pedal must be depressed.

• A/T: Transmission in position.

ECM CONNECTORS

Measure voltage between ECM

connector terminals C6 and A26

with the ignition switch in the

start position.

WIRE SIDE OF FEMALE TERMINALS

Is there battery voltage?

Is the fuse OK?
Repair short in the wire

between the ECM (C6) and

the No. 7 STARTER SIGNAL

(7.5 A) fuse or the PGM-FI

main relay.

Replace the No. 7 STARTER

SIGNAL (7.5 A) fuse.
Starter switch signal is OK.

Repair open in the wire between

the ECM
(C6)
and the No. 7

STARTER SIGNAL (7.5 A) fuse.
Inspect the No. 7 STARTER SIG-

NAL (7.5 A) fuse in the under-

dash fuse box.ProCarManuals.com

Fuel Suppl y Syste m
PGM-F I Mai n Rela y
Troubleshootin g
Is ther e continuity ?
Chec k fo r a n ope n o r shor t i n th e
wire :Measur e voltag e betwee n th e
PGM-F I mai n rela y 4 P connecto r
terminal No . 3 an d bod y ground .
Is ther e batter y voltage ?
Chec k fo r a n ope n o r shor t i n th e
wire :
1. Tur n th e ignitio n switc h O N (II) .2. Measur e voltag e betwee n th e
PGM-F I mai n rela y 8 P connec -
tor termina l No . 5 an d bod yground .
PGM-FI MAI N RELA Y 8 P CONNECTO R
WIR E SID E O F FEMAL E TERMINAL S
Repai r ope n i n th e wir e betwee n
th e PGM-F I mai n rela y an d G10 1
(locate d a t righ t middl e o fengine) .
PGM-FI MAI N RELA Y 4 P CONNECTO R
Replac e th e ACG(S ) (2 0 A )
fus e i n th e engin e compart -
men t fuse/rela y box .
Repai r ope n o r shor t i n th e
wir e betwee n th e PGM-F Imain rela y an d th e ACG(S )
(2 0 A ) fuse . WIR
E SID E O F FEMAL E TERMINAL S
I s ther e batter y voltage ?
(T o pag e 11-145 ) Replac
e th e No . 2 FUE L
PUMP , SR S 2 (1 5 A ) fus e i n
th e under-das h fus e box .
Repai r ope n o r shor t i n th e
wir e betwee n th e PGM-F Imain rela y an d th e No . 2 FUE L
PUMP , SR S 2 (1 5 A ) fuse .
Engin
e wil l no t start .
Inspectio n o f PGM-F I mai n
rela y an d rela y harness .
Chec k fo r a n ope n in th e wire :
1. Tur n th e ignitio n switc h OFF .2. Disconnec t th e PGM-F I mai n
rela y 4 P connecto r an d 8 P
connector .
3 . Chec k fo r continuit y betwee n
th e PGM-F I mai n rela y 8 P
connecto r termina l No . 7 an d
body ground .
ProCarManuals.com

(From pag e 11-144 )
Chec k fo r a n ope n in th e wire :
Measur e voltag e betwee n th e
PGM-F I mai n rela y 4 P connecto r
termina l No . 4 an d bod y ground . PGM-F
I MAI N RELA Y 4 P CONNECTO R
I s ther e batter y voltage ? —
Replac e th e I G COI L (3 0 A )
fus e i n th e engin e compart -
men t fuse/rela y box .
— Repai r ope n o r shor t i n th e
wir e betwee n th e PGM-F I
mai n rela y an d th e I G COI L
(3 0 A ) fuse . WIR
E SID E O F FEMAL E TERMINAL S
Chec k fo r a n ope n o r shor t i n th e
wire :
1 . Tur n th e ignitio n switc h t o th e
STAR T (III ) position .
NOTE:• M/T : Clutc h peda l mus t b e
depressed .
• A/T : Transmissio n in
position .
2 . Measur e th e voltag e betwee n
th e PGM-F I mai n rela y 8 P con -
necto r termina l No . 3 an d
bod y ground . PGM-F
I MAI N RELA Y 8 P CONNECTO R
WIR E SID E O F FEMAL E TERMINAL S
I s ther e batter y voltage ? —
Replac e th e No . 7 STARTE R
SIGNA L (7. 5 A ) fus e i n th e
under-das h fus e box .
— Repai r ope n o r shor t i n th e
wir e betwee n th e PGM-F I
mai n rela y an d th e No . 7
STARTE R SIGNA L (7. 5 A ) fuse .
Chec k fo r a n ope n in th e wire :
1 . Tur n th e ignitio n switc h OFF .
2 . Disconnec t th e EC M connec -
to r A (2 6 P ) fro m th e ECM .
3 . Chec k fo r continuit y betwee n
th e PGM-F I mai n rela y 8 P
connecto r termina l No . 2 an d
EC M connecto r termina l A4 .
WIRE SID E O F FEMAL E TERMINAL S
I s ther e continuity ? Repai
r ope n i n th e wir e betwee n
th e EC M (A4 ) an d th e PGM-F I
mai n relay .
(T o pag e 11-146 )
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Intake Air System

System Description

The system supplies air for all engine needs. It consists of the intake air pipe, Air Cleaner (ACL), intake air duct, throttle

body, and intake manifold. A resonator in the intake air duct provides additional silencing as air is drawn into the system.

IAB CONTROL

SOLENOID VALVE

To No. 5 BACK-UP LIGHTS

ALTERNATOR TURN SIGNALS

(15 A) FUSE

IAB

CONTROL

DIAPHRAGM

IAB

CONTROL

VALVE
THROTTLE

VALVE
INTAKE

AIR DUCT
ACL
RESONATOR
VARIOUS

SENSORS

INTAKE

MANIFOLDProCarManuals.com