ACURA NSX 1991 Service Repair Manual

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 .
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(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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PGM-FI Syste m
Engine Contro l Modul e (ECM )
(From pag e 11-63 )
Chec k fo r a shor t i n th e A P sen -
sor:1. Tur n th e ignitio n switc h OFF .2. Connec t th e SC S servic e con -
nector .
3 . Disconnec t th e A P senso r 3 P
connector .
4. Tur n th e ignitio n switc h O N (II) .
Is DT C P124 6 and/o r P124 7
indicated ?
Chec k fo r a shor t i n th e wire s
(VC C lines) :
1. Tur n th e ignitio n switc h OFF .2. Disconnec t th e EC M connec -tor D (22P ) an d F (26P) .3. Chec k fo r continuit y betwee nbody groun d an d EC M con -necto r terminal s D10 , F 1 an dF14 individually .
Is ther e continuity ?
I s ther e batter y voltage ?
Chec k fo r a n ope n i n th e wire s
(L G lines) :
1 . Reconnec t al l senso r connec -
tors.2. Reconnec t th e EC M connecto rD (22P ) F (26P) .3. Tur n th e ignitio n switc h O N (II) .4. Measur e voltag e betwee n
bod y groun d an d EC M connec -
tor terminal s A2 6 an d B 9 indi -vidually .
I s ther e les s tha n 1. 0 V ?
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 .
Replac e th e A P sensor .
Repai r shor t t o bod y groun d
in th e wir e betwee n EC M(D10 ) an d throttl e angl e sen -
so r an d EG R valv e lif t sensor .
Repai r shor t t o bod y groun d in
th e wir e betwee n EC M (F1 )and MA P senso r o r Accelerato r
Positio n sensor .
Repai r shor t t o bod y groun d in
th e wir e betwee n EC M (F14 )
an d Accelerato r Positio n sen -
sor.
WIR E SID E O F FEMAL E TERMINAL S
Repai r ope n i n th e wire(s )
between EC M (A13 , C D an dPGM-F I mai n relay .
Chec k fo r poo r connection s
o r loos e wire s a t th e PGM-F I
mai n relay .
ECM CONNECTOR S
WIR E SID E O F FEMAL E TERMINAL S
Repai r ope n i n th e wire(s )
between EC M (A26 , B9 ) an dG10 1 tha t ha d mor e tha n 1. 0 V .
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Drive By Wire System

System Description

The Drive By Wire System is an electronic throttle control system.

This system consists of the throttle valve control motor and Throttle Position (TP) sensor assembled in Throttle Body (TB),

the accelerator position sensor, and the Engine Control Module (ECM).

To THROTTLE

VALVE CONTROL

MOTOR RELAY

THROTTLE

VALVE

CONTROL

MOTOR

Drive By Wire System Functions:

Idle Control Function

When the engine is idling, the ECM controls the throttle valve control motor to maintain the proper idle speed according

to engine loads.

Acceleration Control Function

When the accelerator pedal is depressed, the ECM opens the throttle valve depending on the accelerator position sensor

signals.ProCarManuals.com

Drive B y Wir e Syste m
System Descriptio n
Cruise Contro l Functio n
Th e EC M control s th e throttl e valv e contro l moto r t o maintai n th e se t spee d whe n th e cruis e contro l syste m is operating .
Th e throttl e valv e contro l moto r take s th e plac e o f th e cruis e contro l actuator .
Tractio n Contro l Syste m (TCS ) Functio n
I f whee l spi n occur s durin g acceleratio n o r cornering , th e TC S contro l uni t request s th e EC M to reduc e th e engin e powe r
b y retardin g th e ignitio n timin g an d closin g th e throttl e valve . I f th e wheel s loc k during deceleration , th e TC S contro l uni t
signal s th e EC M to ope n th e throttl e valve .
Engin e Protectio n Functio n
Whe n th e engin e spee d exceed s 8,00 0 rp m (M/T ) o r 7,50 0 rp m (A/T) , th e EC M control s th e throttl e valve , regardles s o f th e
accelerato r position , t o protec t th e engin e fro m over-revving .
Fail-saf e Functio n
O n thi s system , th e EC M monitor s th e positio n o f th e accelerato r peda l wit h a dua l circui t typ e accelerato r positio n sensor ,
an d monitor s th e operatio n o f th e throttl e valv e contro l moto r wit h a Throttl e Positio n (TP ) sensor .
Whe n a n abnormalit y occur s i n th e system , th e EC M restrict s th e operatio n o f th e throttl e valv e contro l moto r t o allo w th e
engin e t o continu e t o run .
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Idle Contro l Syste m
Air Conditionin g Signa l
This signal s th e EC M whe n ther e is a deman d fo r coolin g fro m th e ai r conditionin g system .
Inspectio n o f Ai r Conditionin g
Signal .
ECM CONNECTOR S
Chec k fo r a shor t i n th e circuit :
1. Tur n th e ignitio n switc h OFF .2. Disconnec t th e 12 P connecto rfrom th e coolin g fa n contro lunit.3. Tur n th e ignitio n switc h O N (II) .4. Measur e voltag e betwee n EC M
connecto r terminal s C 2 an d
A26 .WIR E SID E O F FEMAL E TERMINAL S
I s ther e approx . 1 0 V ? Chec
k fo r a shor t i n th e wire :
1. Tur n th e ignitio n switc h OFF .2. Disconnec t th e EC M connec -tor C (12P ) fro m th e ECM .3. Chec k fo r continuit y betwee n
EC M connecto r termina l C 2
an d bod y ground .
I s ther e continuity ? —
Repai r shor t i n th e wir e
betwee n th e EC M (C2 ) an d th e
coolin g fa n contro l unit .
— Se e th e ai r conditione r inspec -
tio n (se e sectio n 22 ).
Substitut e a known-goo d EC M
an d recheck . I f prescribe d volt -
ag e i s no w available , replac e
th e origina l ECM .
Se e th e ai r conditione r inspec -
tio n (se e sectio n 22 ).
Chec k fo r a n ope n in th e circuit :
1. Tur n th e ignitio n switc h OFF .2. Reconnec t th e 12 P connecto r t o
th e coolin g fa n contro l unit .
3. Tur n th e ignitio n switc h O N (II) .4. Momentaril y connec t EC M
connecto r terminal s A 8 t o
A2 6 severa l time s wit h ajumpe r wire .
(To pag e 11-118 )
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Idle Contro l Syste m
Air Conditionin g Signa l
(From pag e 11-117 )
I s ther e a clickin g nois e fro m th e
A/ C compresso r clutch ?
Chec k fo r th e operatio n o f th e
A/C :1. Star t th e engine .
2 . Tur n th e blowe r switc h ON .
3 . Tur n th e A/ C switc h ON .
Doe s th e A/ C operate ?
Ai r conditionin g signa l i s OK . A/
C CLUTC H RELA Y 4P CONNECTO R
Chec k fo r a n ope n in th e wire :
Momentaril y connec t th e No . 4 ter -
mina l o f th e 4 P connecto r o n th e
A/ C clutc h rela y t o bod y groun d
severa l times .
WIRE SID E O F
FEMAL E TERMINAL S
I s ther e a clickin g nois e fro m th e
A/ C compresso r clutch ? Se
e ai r conditione r inspectio n (se e
sectio n 22 ).
Repai r ope n in th e wir e betwee n
th e EC M (AS ) an d th e A/ C clutc h
relay.
ECM CONNECTOR S
Chec k fo r a n ope n in th e wire :
Measur e voltag e betwee n EC M
connecto r terminal s C 2 an d A26 . WIR
E SID E O F FEMAL E TERMINAL S
I s voltag e les s tha n 1. 0 V ? Repai
r ope n in th e wir e betwee n
th e EC M (C2 ) an d th e A/ C switch .
Substitut e a known-goo d EC M
an d recheck . I f symptom/indi -
catio n goe s away , replac e th e
origina l ECM .
Se e th e ai r conditione r inspec -
tio n (se e sectio n 22 ).
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Alternator (ALT ) F R Signa l
This signal s th e EC M whe n th e Alternato r (ALT ) i s charging .
Inspection o f AL T F R Signal .
ECM CONNECTOR S
WIR E SID E O F FEMAL E TERMINAL S
Chec k fo r a shor t i n th e wire :
1. Tur n th e ignitio n switc h OFF .2. Disconnec t th e negativ e bat -
ter y cabl e fro m th e battery .
3 . Disconnec t th e EC M connec -
tor D (22P ) fro m th e ECM .4. Chec k fo r continuit y betwee n
EC M connecto r termina l D 5
an d bod y ground .
I
s ther e approx . 5 V ?
Chec
k fo r a shor t i n th e circuit :
1 . Disconnec t th e GR N 4 P con -
necto r fro m th e ALT .
2. Tur n th e ignitio n switc h O N (II) .3. Measur e voltag e betwee n EC M
connecto r terminal s D 5 an d
A26 .
Is ther e continuity ? Repai
r shor t i n th e wir e betwee nthe EC M (D5 ) and th e ALT .
Substitut e a known-goo d EC M
an d recheck . I f prescribe d voltag e
i s no w available , replac e th e origi -
nal ECM .Chec k th e operatio n o f th e ALT :1. Tur n th e ignitio n switc h OFF .2. Reconnec t th e AL T GR N 4 P
connecto r t o th e ALT .
3 . Star t th e engine . Hol d th e
engin e a t 3,00 0 rp m wit h n oloa d (A/ T in position ,M/T in neutral ) unti l th e radiato r
fa n come s on , the n le t i t idle .
4 . Measur e voltag e betwee n EC M
connecto r terminal s D 5 an d
A26.
Doe s th e voltag e decreas e whe nhead light s an d rea r defogge r ar eturne d on ? AL
T F R signa l i s OK .
(T o pag e 11-120 )
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Idle Contro l Syste m
Alternato r (ALT ) F R Signa l
(From pag e 11-119 )
ALT GR N 4P CONNECTO R
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 negativ e batter y
cabl e fro m th e battery .
3 . Disconnec t th e EC M connec -
tor D (22P ) fro m th e ECM .4. Disconnec t th e GR N 4 P con -
necto r fro m th e ALT .
5 . Connec t No . 2 termina l t o bod y
groun d wit h a jumpe r wire .6. Chec k fo r continuit y betwee n
EC M connecto r termina l D 5
and bod y ground .
WIRE SID E O F FEMAL E TERMINAL S
EC M CONNECTO R D (22P )
I s ther e continuity ? Repai
r ope n i n th e wir e betwee n
the EC M (D5 ) and th e ALT .
WIRE SID E O F FEMAL E TERMINAL S
Se e th e AL T inspectio n (se e
sectio n 23 ).
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Inspection o f A/ T Gea r Positio nSignal.
This signal s th e EC M whe n th e transmissio n is in position.
Automati c Transaxl e (A/T ) Gea r Positio n Signa l
Check th e operatio n o f th e A/ T
gea r positio n switch :
1 . Tur n th e ignitio n switc h O N (II) .
2 . Observ e th e A/ T shif t positio n
indicato r an d selec t eac h posi -
tio n separately .
Doe s th e indicato r ligh t prop -
erly?See th e A/ T gea r positio n indica -
to r inspectio n (se e sectio n 14 ).
ECM CONNECTOR S
WIR E SID E O F FEMAL E TERMINAL S
Chec k fo r a shor t i n th e wire :
1. Tur n th e ignitio n switc h OFF .2. Disconnec t th e EC M connecto r
B (16P ) fro m th e ECM .
3 . Chec k fo r continuit y betwee n
ECM connecto r termina l B 4an d bod y ground .
Is ther e approx . 5 V ?
Chec
k fo r a shor t i n th e circuit :
1 . Tur n th e ignitio n switc h OFF .
2 . Disconnec t th e 30 P (C412 )
connecto r fro m th e gaug e
assembly .
3 . Disconnec t th e 26 P connecto r
fro m th e TCM .
4 . Tur n th e ignitio n switc h O N (II) .
5 . Measur e voltag e betwee n
EC M connecto r terminal s B 4
and A26 .
Is ther e continuity ? Repai
r shor t i n th e wir e betwee n
th e EC M (B4 ) an d th e gaug eassembly .
Substitute a known-goo d EC M
an d recheck . I f prescribe d voltag e
i s no w available , replac e th e origi -
nal ECM .(To pag e 11-122 )
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