engine ACURA TL 1995 Service Manual PDF

Troubleshooting
Troubleshooting Procedure s (cont'd )
DataDescriptio nOperating Valu e
Freeze Dat a
HO2 S
Feedbac k
Loop Statu s
(Bank 1 : Right )
(Bank 2 : Left )
Loop statu s i s indicate d a s "open " o r "closed" .
Closed: Based o n th e HO2 S output , th e PC M deter -
mine s th e air/fue l rati o an d control s th e amoun t o f
injecte d fuel .
Open : Ignorin g H02 S output , th e PC M refer s t o signal s
fro m th e TP , MAP , an d EC T sensor s to contro l th e
amoun t o f injecte d fuel . A
t idl e speed : close d
Shor t Ter m
Fue l Tri m
(Ban k 1 : Right )
(Bank 2 : Left )
The air/fue l rati o correctio n coefficien t fo r correctin g
th e amoun t o f injecte d fue l whe n HO2 S feedbac k is in
th e close d loo p status . Whe n th e signa l fro m th e HO2 S
i s weak , shor t ter m fue l tri m get s higher , an d th e PC M
increase s th e amoun t o f injecte d fuel . Th e air/fue l rati o
graduall y get s richer , causin g a highe r HO2 S output .
Consequently , th e shor t ter m fue l tri m is lowered , an d
th e PC M reduce s th e amoun t o f injecte d fuel . Thi s
cycl e keep s th e air/fue l rati o close to th e stoichiometri c
rati o whe n in close d loo p status .-30%-+43 %
Long Ter m
Fue l Tri m
(Ban k 1 : Right )
(Ban k 2 : Left ) Lon
g ter m fue l tri m in compute d fro m shor t ter m fue l
tri m an d indicate s change s occurrin g in th e fue l suppl y
syste m ove r a lon g period .
If lon g ter m fue l tri m is highe r tha n 1.00 , th e amoun t o f
injecte d fue l mus t b e increased . I f i t i s lowe r tha n 1.00 ,
th e amoun t o f injecte d fue l mus t b e reduced .
-19%-+25 %
Intake Ai r
Temperatur e
(IAT)
The IA T senso r convert s intak e ai r temperatur e int o
voltag e an d signal s th e PCM . Whe n intak e ai r tempera -
tur e is low , th e interna l resistanc e o f th e senso r
increases , an d th e voltag e signa l i s higher . Wit
h col d engine :
Sam e a s ambien t temper -
atur e an d EC T
Throttl e
Positio n Base
d o n th e accelerato r peda l position , th e openin g
angl e o f th e throttl e valv e is indicated . A
t idle : Approx . 10 %
At ful l throttle : Approx .
90%
Ignitio n
Timing
The ignitio n advanc e angl e is se t b y th e PCM . Th e PC M
matche s ignitio n timin g t o th e drivin g conditions .A
t idl e speed : 1 5 + 2°
BTD C wit h th e SC S servic e
connecto r connected .
Calculated
Load Valu e
(CLV )
CLV is th e engin e loa d calculate d fro m th e MA P data . At idl e speed :
15-35 %
A t 2,50 0 rp m wit h n o load :
12-30 %
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PGM-FI System

System Description (cont'd)

3. Fuel Cut-off Control

During deceleration with the throttle valve closed, current to the fuel injectors is cut off to improve fuel economy at

speeds over 1,000 rpm.

Fuel cut-off action also takes place when engine speed exceeds 6,500 rpm, regardless of the position of the throttle

valve, to protect the engine from over-revving.

4. A/C Compressor Clutch Relay .

When the PCM receives a demand for cooling from the air conditioning system, it delays the compressor from being

energized, and enriches the mixture to assure a smooth transition to the A/C mode.

5. Evaporative Emission (EVAP) Purge Control Solenoid Valve

'96 model: When the engine coolant temperature is below 158°F (70°C), the PCM controls the EVAP purge control

solenoid valve which cuts vacuum to the EVAP purge control canister diaphragm.

'97 - 98 models: When the engine coolant temperature is above 99°F (37°C), the PCM controls the EVAP purge control

solenoid valve which controls vacuum to the EVAP purge control canister.

6. Intake Air Bypass (IAB) Low Control Solenoid Valve, Intake Air Bypass (IAB) High Control Solenoid Valve

When engine speed is below 3,350 rpm, the IAB High Control Solenoid Valve and IAB Low Control Solenoid Valve are

activated by a signal from the PCM. Intake air flows through a long chamber path, increasing torque at low RPM.

When engine speed is 3,350 - 3,950 rpm, the IAB Low Control Solenoid Valve is deactivated by the PCM. Intake air

flows through a short chamber path, increasing mid-range torque.

When the engine rpm is above 3,950 rpm, the IAB Low Control Solenoid Valve and IAB High Control Solenoid Valve are

deactivated by the PCM. This creates a very short intake path and increases high-speed torque.

7. Exhaust Gas Recirculation (EGR) Control Solenoid Valve

When the EGR is required for control of oxides of nitrogen (NOx) emissions, the PCM controls the EGR control solenoid

valve which supplies regulated vacuum to the EGR valve.

ECM Fail-safe/Back-up Functions

1. Fail-safe Function

When an abnormality occurs in a signal from a sensor, the PCM ignores that signal and assumes a pre-programmed

value for that sensor that allows the engine to continue to run.

2. Back-up Function

When an abnormality occurs in the PCM itself, the fuel injectors are controlled by a back-up circuit independent of the

system in order to permit minimal driving.

3. Self-diagnosis Function [Malfunction Indicator Lamp (MIL)]

When an abnormality occurs in a signal from a sensor, the PCM supplies ground for the MIL and stores the DTC in

erasable memory. When the ignition is initially turned on, the PCM supplies ground for the MIL for two seconds to

check the MIL bulb condition.

4. Two Driving Cycle Detection Method

To prevent false indications, the two driving cycle detection method is used for the H02S, fuel metering-related, idle

control system, ECT sensor, EGR system, TWC, EVAP control system and other self-diagnostic functions. When an

abnormality occurs, the PCM stores it in its memory. When the same abnormality recurs after the ignition switch is

turned OFF and ON (II) again, the PCM informs the driver by lighting the MIL.

However, to ease troubleshooting, this function is cancelled when you short the service check connector. The MIL will

then blink immediately when an abnormality occurs.ProCarManuals.com

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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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.
ProCarManuals.com

(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

(From pag e 11-108 )
Chec k fo r a n ope n in th e wir e (AT P
P N line) :
1. Tur n th e ignitio n switc h OFF .2. Reconnec t th e 16 P connecto r
t o th e gaug e assembly .
3 . Star t th e engine .
4 . Measur e voltag e betwee n PC M
connecto r terminal s E2 4 an d
A26 wit h th e transmissio n inposition .
PCM CONNECTOR S
A (26P)E (26P)
Wire sid e o f femal e terminal s
I s ther e les s tha n 1. 0 V ? Repai
r ope n in th e wir e betwee n
the PC M (E24 ) an d the gaug e
assembly .
Check fo r a n ope n in th e wir e (AT PPN line) :Measur e voltag e betwee n PC M
connecto r terminal s E2 4 an d A2 6
with th e transmissio n i n posi -tion.
Is ther e les s tha n 1. 0 V ? Repai
r ope n in th e gaug e assem -bly.
A/T gea r positio n signa l i s OK .
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