ACURA TL 1995 Service Repair Manual

Powertrain Control Module (PCM)

NOTE: If this symptom is intermittent, check for a loose fuse No. 1 (BACK UP

LIGHTS, METER LIGHTS, 10 A) in the under-dash fuse/relay box, a poor con-

nection at PCM terminal A7, or an intermittent open in the GRN/RED wire

between the PCM (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 (MIL line):

1. Turn the ignition switch OFF.

2. Connect the PCM 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 PCM,

and recheck. If symptom/indica-

tion goes away, replace the origi-

nal
PCM.
— Repair short or open in the

wire between NO. 1 (BACK-UP

LIGHTS, METER LIGHTS) (10

A) fuse and gauge assembly.

— Replace No. 1 (BACK-UP

LIGHTS, METER LIGHTS) (10 A)

fuse.

PCM CONNECTOR A (26P)

Check for an open in the wires

(PG1, PG2 lines):

1. Turn the ignition switch ON (II).

2. Measure voltage between

body ground and PCM con-

nector terminals A12 and A25

individually.
Wire side of female terminals

Is there less than 1.0 V?
Repair open in the wire(s)

between PCM and G101 (located

at intake manifold) that had

more than 1.0 V.

PCM CONNECTOR A (26P)

JUMPER WIRE

Wire side of female terminals
Repair open in the wires

between PCM (A7) and gauge

assembly.

Replace the MIL bulb.
Substitute a known-good PCM

and recheck. If symptom/indica-

tion goes away, replace the origi-

nal
PCM.
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
Powertrai n Contro l Modul e (PCM ) (cont'd )
The Malfunctio n Indicato r Lam p
(MIL ) stay s o n o r come s o n afte r
tw o seconds .
Chec k th e Diagnosti c Troubl e
Code (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 .
Are an y DTC(s ) indicated ?
Check 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 ?
Tr y t o star t th e engine .
Doe s th e engin e start ?
NOTE :When ther e is n o Diagnosti c Troubl e Cod e (DTC ) stored , th e MI L wil l sta y o n if th e SC S servic e
connecto r i s connecte d an d th e ignitio n switc h is on .
I f thi s sympto m is intermittent , chec k for :
— A loos e EC U (PCM ) (2 0 A ) fus e in th e under-hoo d fuse/rela y bo x
— A loos e No . 2 FUE L PUM P (1 0 A ) fus e in th e under-das h fuse/rela y bo x
— A n intermitten t shor t i n th e wire betwee n th e PC M (C5 ) an d th e servic e chec k connecto r
— A n intermitten t shor t i n th e wire betwee n th e PC 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 PC M (D10 ) an d th e MA P senso r
— A n intermitten t shor t i n th e wire betwee n th e PC M (D21 ) an d th e T P sensor , EG R valv e lif t
sensor , TC S contro l valv e angl e sensor , Fue l tan k pressur e sensor *
Se e th e OB D II sca n too l o r Hond a PG M Teste r user' s manual s fo r specifi c operatin g instruc -
tions.: '9 7 - 9 8 model s
G o to troubleshootin g procedures .
(se e pag e 11-32 )
Repai r ope n o r shor t i n wir e
betwee n the PCM (D4 ) an d
Dat a Lin k Connector .
G o to troubleshootin g proce -
dures . (se e pag e 11-32 )
PCM CONNECTO R C (12P )
Chec k fo r a shor t i n th e wir e (SC S
line) :
1 . Sto p th e engin e an d tur n th e
ignitio n switc h O N (II) .2. Measur e voltag e betwee n th e
PC M connecto r termina l C 5
an d bod y ground . (T
o pag e 11-55 )
Wire sid e o f femal e terminal s
I s ther e approx . 5 V ?
(T o pag e 11-55 ) Repai
r shor t t o bod y groun d in
th e wir e betwee n PC M (C5 ) an d
servic e chec k connector .
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(From pag e 11-54 )
Chec k fo r a shor t i n th e wir e (MI L
line) :
1. Tur n th e ignitio n switc h OFF .2. Disconnec t th e PC 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 PC M (A7 )
and MIL .
Substitut e a known-goo d PC Mand recheck . I f symptom/indica -
tio n goe s away , replac e th e origi -
nal PCM .
(From pag e 11-54 )
I s th e fus e OK ?
Inspec t IG 1 I G COI L (3 0 A ) fus e in
th e ignitio n coi l fus e holde r box . Repai
r shor t i n th e wir e
betwee n EC U (PCM ) (2 0 A )
fus e an d PGM-F I mai n relay .
Replac e EC U (PCM ) (2 0 A )
fuse .
Is th e fus e OK ? Repai
r shor t i n th e wir e
betwee n IG 1 I G COI L (3 0 A )
fus e an d PGM-F I mai n relay .
Replac e IG 1 I G COI L (3 0 A )
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
TC S contro l valv e angl e sen -
sorFue l tan k pressur e senso r('97-98 models )
Does th e MI L g o OF F momen -
tarily ? Replac
e th e senso r tha t cause dthe ligh t t o g o out .
(To pag e 11-56 )
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PGM-FI Syste m
Powertrai n Contro l Modul e (PCM ) (cont'd )
(From pag e 11-55 )
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 PC M connec -
tor D (22P) .3. Chec k fo r continuit y betwee nbody groun d an d PC M con -necto r terminal s D1 0 an d D2 1individually .
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 PC M connecto r
D (22P) .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 PC M connec -
to r 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 PC M
an d recheck . I f symptom/indica -
tio n goe s away , replac e th e origi -
nal PCM .
PCM CONNECTO R D (22P )
Repai r shor t t o bod y groun d
i n th e wir e betwee n PC M
(D10 ) an d MA P sensor .Repair shor t t o bod y groun d in
th e wir e betwee n PC M (D21 )
an d EG R valv e lif t sensor , T P
sensor , TC S contro l valv e
angl e senso r o r fue l tan k pres -
sur e senso r ('9 7 - 9 8 models) .Wir
e sid e o f femal e terminal s
A (26P)
PCM CONNECTOR S
Repair ope n i n th e wire(s )
betwee n PC M (A13 , B1 ) an d
PGM-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 .
Tes t th e PGM-F I mai n rela y
(se e pag e 11-129 ). Wir
e sid e o f femal e terminal s
PCM CONNECTOR S
A (26P)B (16P)
Repai r ope n i n th e wire(s )
betwee n PC M (A26 , B9 ) an d
G10 1 tha t ha d mor e tha n 1. 0 V .Wir e sid e o f femal e terminal s
Check fo r a n ope n i n th e wire s
(IG P lines) :
1 . Tur n th e ignitio n switc h O N (II) .
2 . Measur e voltag e betwee n bod y
groun d an d PC M connecto r
terminal s A1 3 an d B 1 individu -
ally .B (16P )
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Idle Control System

System Description

The idle speed of the engine is controlled by the Idle Air Control (IAC) Valve.

The valve changes the amount of air bypassing into the intake manifold in response to electric current controlled by the

PCM. When the IAC Valve is activated, the valve opens to maintain the proper idle speed.

ENGINE

COOLANT

IAC VALVE

INTAKE

MANIFOLD
PCM
From

PGM-FI

MAIN

RELAY

FAST

IDLE

THERMO

VALVE
IDLE

ADJUSTING

SCREW
VARIOUS

SENSORS

ENGINE

COOLANTProCarManuals.com

Idle Contro l Syste m
System Descriptio n (cont'd )
1. Afte r th e engine starts, th e IA C valv e open s fo r a certai n time . Th e amoun t o f ai r i s increase d t o rais e th e idl e spee d
about 150-30 0 rpm .
2. Whe n th e coolan t temperatur e i s low , th e IA C valv e i s opene d t o obtai n th e prope r fas t idl e speed . Th e amoun t o f
bypasse d ai r i s thu s controlle d i n relatio n t o th e engin e coolan t temperature .
IDLE SPEE D(rpm)
ENGIN ECOOLAN T TEMPERATUR E
3. Whe n th e idl e spee d i s ou t o f specificatio n an d th e sca n too l doe s no t indicat e Diagnosti c Troubl e Cod e (DTC ) P050 5 o r
P1508 , chec k th e followin g items :
Adjus t th e idl e spee d (se e pag e 11-114 )
Ai r conditionin g signa l (se e pag e 11-104 )
AL T F R signa l (se e pag e 11-106 )
Starte r switc h signa l (se e pag e 11-107 )
A/ T gea r positio n signa l (se e pag e 11-108 )
PS P switc h signa l (se e pag e 11-110 )
Brak e switc h signa l (se e pag e 11-112 )
Fas t idl e therm o valv e (se e pag e 11-113 )
Hose s an d connection s
IA C valv e an d it s mountin g O-ring s
4 . I f th e abov e item s ar e normal , substitut e a known-goo d IA C valv e an d readjus t th e idl e spee d (se e pag e 11-114 ).
I f th e idl e spee d stil l canno t b e adjuste d t o specificatio n (an d th e sca n too l doe s no t indicat e DT C P050 5 o r P1508 )
afte r IA C valv e replacement , substitut e a known-goo d PC M an d recheck . I f sympto m goe s away , replac e th e origina l
PCM.
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Idle Contro l Syste m
Air Conditionin g Signa l
This signal s th e PC 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 .
Chec k fo r a shor t i n th e wir e
(AC S line) :
1 . Tur n th e ignitio n switc h OFF .
2 . Disconnec t th e A/ C pressur e
switc h A connecto r an d radia -
to r fa n diod e connector .
3 . Tur n th e ignitio n switc h O N (II) .
4 . Measur e voltag e betwee n
PC M connecto r terminal s C 2
and A26 .
Is ther e batter y voltage ?
Chec k fo r a n ope n i n th e wir e
(ACC line) :1. Tur n th e ignitio n switc h OFF .
2 . Reconnec t th e A/ C pressur e
switc h A connecto r an d radia -
to r fa n diod e connector .
3 . Tur n th e ignitio n switc h O N (II) .
4 . Momentaril y connec t PC M
connecto r terminal s A 8 an d
A2 6 wit h a jumpe r wir e sever -
a l times .
(T o pag e 11-105 )
A (26P)
PCM CONNECTOR S
C (12P )
Wire sid e o f femal e terminal s
Chec k fo r a shor t i n th e wir e (AC S
line):1. Tur n th e ignitio n switc h OFF .
2 . Disconnec t th e PC M connec -
tor C (12P) .3. Chec k fo r continuit y betwee n
bod y groun d an d PC M con -
necto r termina l C2 .
I s ther e continuity ? Repai
r shor t i n th e wir e betwee n
th e PC M (C2 ) an d th e A/ C pres -
sur e switc h A or radiato r fa n
diode .
Substitut e a known-goo d PC M
an d recheck . I f prescribe d volt -
ag e is no w available , replac e
th e origina l PCM .
Se e th e ai r conditione r inspec -
tio n (se e sectio n 22 ).
PCM CONNECTO R A (26P )
Wir e sid e o f femal e
terminal s
JUMPERWIRE
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(From pag e 11-104 )
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 . Chec
k fo r a n ope n i n th e wir e
(ACC line) :Momentaril y connec t th e A/ C
clutc h rela y 4 P connecto r termi -
nal No . 2 to bod y groun d wit h ajumpe r wir e severa l times . A/
C CLUTC H RELA Y CONNECTO R (C308 )
JUMPE RWIRE
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 PC M (A8 ) an d th e A/ C clutc h
relay.
PCM CONNECTOR S
A (26P)
Chec k fo r a n ope n i n th e wir e
(AC S line) :
Measur e voltag e betwee n PC M
connecto r terminal s A2 6 an d C2 . 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 i n th e wir e betwee n
th e PC M (C2 ) an d th e A/ C pres -
sur e switc h A or radiato r fa n
diode .
Substitut e a known-goo d PC M
an d recheck . I f symptom/indi -
catio n goe s away , replac e th e
origina l PCM .
Se e th e ai r conditione r inspec -
tio n (se e sectio n 22 ).
C (12P )
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Idle Contro l Syste m
Alternato r (ALT ) F R Signa l
This signal s th e PC M whe n th e Alternato r (ALT ) i s charging .
Is ther e approx . 5 V ?
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 o
loa d (transmissio n in o r
position ) 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 PC M
connecto r terminal s D 5 an d A26 .
Doe s th e voltag e decreas e whe n
headlight s an d rea r defogge r ar e
turne d on ?
Chec k fo r a n ope n in th e wir e (AL T
F line) :
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 PC M connec -
tor D (22P) .4. Disconnec t th e GR N 4 P con -
necto r fro m th e ALT .
5 . Connec t th e AL T 4 P connecto r
termina l No . 2 to bod y groun d
with a jumpe r wire .6. Chec k fo r continuit y betwee n
bod y groun d an d PC M con -
necto r termina l D5 .
I s ther e continuity ?
Se e th e AL T inspectio n (se e
sectio n 23 ).
PC M CONNECTOR S
A (26P)D (22P )
LG1 (BRN/BLK )
Wire sid e o f femal e terminal s
Chec k fo r a shor t i n th e wir e (AL T
F line) :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 PC M connecto r
D (22P) .4. Chec k fo r continuit y betwee n
bod y groun d an d PC M con -
necto r termina l D5 .
D (22P )
Is ther e continuity ? Repai
r shor t i n th e wir e betwee nthe PC M (D5 ) and th e ALT .
Substitut e a known-goo d PC M
an d recheck . I f prescribe d voltag e
i s no w available , replac e th e origi -
nal PCM .
ALT F R signa l i s OK .
ALT GR N 4P CONNECTO R (C129 )
JUMPE R WIR E
Wir e sid e o f femal e terminal s
Repai r ope n wir e betwee n th e
PC M (D5 ) and th e ALT .
Wire sid e o f femal e terminal s
PC
M CONNECTO R D (22P )
Chec
k fo r a shor t i n th e wir e (AL T
F line) :
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 PC M
connecto r terminal s D 5 an d A26 .
Inspectio
n o f AL T F R Signal .
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Starter Switch Signal

This signals the PCM when the engine is cranking.

PCM CONNECTORS

A
(26P)
C
(12P)

Wire side of female terminals

Is there battery voltage?

Is the fuse OK?
Repair short in the wire be-

tween the PCM (C6) and the

No. 9 STARTER SIGNAL (7.5

A) fuse or the PGM-FI main

relay.

Replace the No. 9 STARTER

SIGNAL (7.5 A) fuse.

Repair open in the wire between

the PCM
(C6)
and the No. 9

STARTER SIGNAL (7.5 A) fuse.
Starter switch signal is OK.
Inspect the No. 9 STARTER SIG-

NAL (7.5 A) fuse in the under-dash

fuse/relay box.
Check for an open or short in the

wire (STS line):

Measure voltage between PCM

connector terminals C6 and A26

with the ignition switch in the

start position (III).
Inspection of Starter Switch Sig-

nal.
NOTE: Transmission in or position.ProCarManuals.com