ACURA NSX 1991 Service Repair Manual

Page 231 of 1640

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

Page 232 of 1640

(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 )
ProCarManuals.com

Page 233 of 1640

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 .
ProCarManuals.com

Page 234 of 1640


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

Page 235 of 1640

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 .
ProCarManuals.com

Page 236 of 1640

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 )
ProCarManuals.com

Page 237 of 1640

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 ).
ProCarManuals.com

Page 238 of 1640

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 )
ProCarManuals.com

Page 239 of 1640

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 ).
ProCarManuals.com

Page 240 of 1640

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 )
ProCarManuals.com

Page:   < prev 1-10 ... 191-200 201-210 211-220 221-230 231-240 241-250 251-260 261-270 271-280 ... 1640 next >