1991 ACURA NSX lights

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

Idle Contro l Syste m
Idle Spee d Settin g
Inspection/Adjustmen t
NOTE: Befor e settin g th e idl e speed , chec k th e followin g
items :
— Th e Chec k Engin e ligh t ha s no t bee n reporte d on .
— Ignitio n timin g
— Spar k plug s
— Ai r cleane r
— PC V syste m
1 . Star t th e engine . Hol d th e engin e a t 3,00 0 rp m wit h
no loa d (A/ T in position , M/ T in neutral ) unti l
th e radiato r fa n come s on , the n tur n th e ignitio n
switc h OFF .
2 . Connec t th e SC S servic e connecto r t o servic e chec k
connector .
3. Connec t a OBDI I sca n too l (se e pag e 11-38 ) o r
tachometer .
• Connec t a tachomete r t o loo p o f ignite r uni t sec -
ondary , or.. .
TACHOMETE R
Remove th e rubbe r ca p fro m th e tachomete r
connector an d connec t a tachometer .
TACHOMETE R
RUBBERCAP
TACHOMETE RCONNECTOR
4. Restar t th e engine .
5 . Chec k idlin g i n no-loa d condition s i n whic h th e
headlights , blowe r fan , rea r defogger , coolin g fan ,
an d ai r conditione r ar e no t operating .
NOTE : D o no t depres s th e accelerato r peda l i n thi s
step .
Idl e spee d shoul d be :
Adjus t th e idl e speed , i f necessary , b y turnin g th e
idl e adjustin g screw .
NOTE : Afte r adjustin g th e idl e spee d i n thi s step ,
chec k th e ignitio n timin g (se e sectio n 23 ).
I f i t i s ou t o f spec , g o bac k t o ste p 4 .
IDL E ADJUSTIN GSCREW
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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

Intake Air System

Intake Air Bypass (IAB) Control System

Description

Satisfactory power performance is achieved by closing and opening the intake air bypass (IAB) control valves. High torque

at low engine speed is achieved when the valves are closed, whereas high power at high engine speed is achieved when

the valves are opened.

INTAKE AIR BYPASS (IAB) CONTROL

SOLENOID VALVE ON

ENGINE SPEED IS ABOVE 4,800 rpm

OPEN: HIGH ENGINE SPEED

IAB CONTROL

SOLENOID

VALVE

To No. 5 BACK-UP LIGHTS

ALTERNATOR TURN SIGNALS

(15 A) FUSE

IAB

CONTROL

DIAPHRAGM

IAB

CONTROL

VALVE
CLOSED: LOW ENGINE SPEEDProCarManuals.com

Emission Contro l Syste m
System Descriptio n
The emissio n contro l syste m include s tw o Thre e Wa y
Catalyti c Converter s (TWCs) , Exhaus t Ga s Recirculatio n
(EGR ) system , Positiv e Crankcas e Ventilatio n (PCV ) sys -
te m an d Evaporativ e Emissio n (EVAP ) Contro l system .
Th e emissio n contro l syste m is designe d t o mee t federa l
an d stat e emissio n standards .
Tailpipe Emissio n
Inspectio n
Do no t smok e durin g thi s procedure . Kee p
an y ope n flam e awa y fro m you r wor k area .
1 . Star t th e engine . Hol d th e engin e a t 3,00 0 rp m wit h
no loa d (A/ T in position , M/ T in neutral ) unti l
the radiato r fa n come s on , the n le t i t idle .
2 . Connec t a tachometer .
3 . Chec k an d adjus t th e idl e speed , i f necessar y (se e
pag e 11-128 ).
4 . War m u p an d calibrat e th e C O mete r accordin g t o
th e mete r manufacturer' s instructions .
5 . Chec k idl e C O wit h th e headlights , heate r blower ,
rea r windo w defogger , coolin g fan , an d ai r condi -
tione r off .
NOTE : (Canada ) Pul l th e parkin g brak e leve r up .
Star t th e engine , the n chec k tha t th e headlight s ar e
off.
CO mete r shoul d indicat e 0.1 % maximum .
ProCarManuals.com

Evaporative Emission (EVAP) Controls

Description

The evaporative emission controls are designed to minimize the amount of fuel vapor escaping to the atmosphere. The

system consists of the following components:

A. Evaporative Emission (EVAP) Control Canister

An EVAP control canister is used for the temporary storage of fuel vapor until the fuel vapor can be purged from the

EVAP control canister into the engine and burned.

B. Vapor Purge Control System

EVAP control canister purging is accomplished by drawing fresh air through the EVAP control canister and into a port

on the throttle body. The purging vacuum is controlled by the EVAP purge control diaphragm valve and the EVAP

control solenoid valve.

EVAP PURGE CONTROL SOLENOID VALVE OFF AFTER

STARTING ENGINE

ENGINE COOLANT TEMPERATURE ABOVE 153°F (67°C)

To No. 5 BACK-UP LIGHTS

ALTERNATOR TURN SIGNALS

(15 A) FUSE

FRESH

AIR
EVAP

PURGE CONTROL

DIAPHRAGM VALVE
EVAP PURGE

CONTROL

SOLENOID VALVE
EVAP PURGE

FLOW SWITCH
C. Fuel Tank Vapor Control System

When fuel vapor pressure in the fuel tank is higher than the set value of the EVAP two way valve, the valve opens and

regulates the flow of fuel vapor to the EVAP control canister.

EVAP

TWO WAY

VALVE
FUEL

FILL CAPProCarManuals.com

Component Location s
ENGINE CONTRO L MODUL E (ECM )
ABS CONTRO L UNI T
UNDER-HOO D
FUSE/RELA Y BO X
RIGHT-FRON T
WHEE L SENSO R RIGHT-REA
R WHEE L SENSO R
TRANSMISSIO N CONTRO L MODUL E (TCM )
THROTTL E BOD Y
THROTTL E ACTUATO R
LEFT-REARWHEEL SENSO R
TC S SWITC H
LEFT-FRON T
WHEE L SENSO R
TCS CONTRO L UNI T
LATERAL ACCELERATION (Lg) SENSOR
A/T GEA R POSITIO N SWITC H
UNDER-DAS H FUS E BO X
GAUG E ASSEMBL Y UNDER-HOO
D FUSE/RELA Y BO X
BRAK E LIGHTS/HOR N (2 0 A ) FUS E
TC S INDICATO R LIGH T
I G S W (A ) (5 0 A ) FUS E
UNDER-DAS H FUS E BO X CLOC
K (7. 5 A ) FUS E
BACK-U P LIGHTS/ALTERNATOR /
TUR N SIGNAL S (1 5 A ) FUS E
STEERIN
G ANGL E SENSO R
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Troubleshooting

Self-diagnosis Circuit Check
The Automatic Climate Control System has a built-in self diagnosis feature. To run it, turn the ignition switch ON (II),
then turn the fan speed dial to the AUTO position. Set the temperature control dial to 60° F(18°C), then gradually move

0

th
e
dial up the temperature range to 90°F (32°C). At each temperatu\
re setting, push both the AUTO and OFF burtons
o

n
the control unit at the same time. Wait for at least one minute for the\
system to readjust and check for problems.

If any problems are found in circuits "A" through "I", the system will indicate which circuit has the problem by lighting

the respective indicator light.
NOTE: The climate control unit does not memorize which self-diagnosis indicator lights come on. If you turn the ig-

nition switch OFF, the indicator light memory will be lost.

AUTO BUTTON

OFF BUTTON

TEMPERATURE CONTROL DIAL
TEMP DISPLAY


FAN SPEED DIAL

NOTE:
When you turn the ignition switch OFF, the self-diagnosis function will be canceled. After completing repair work, run the self-diagnosis again to make sure that there are no other malfunctions.COMPONENT WITH PROBLEM
IN-CAR TEMPERATURE SENSOR
OUTSIDE AIR TEMPERATURE

SENSOR

SUNLIGHT SENSOR
HEATER CORE TEMPERATURE

SENSOR

EVAPORATOR TEMPERATURE

SENSOR

AIR MIX CONTROL MOTOR
MODE CONTROL MOTOR
RECIRCULATION CONTROL MOTOR
VENT DOOR CONTROL MOTOR
POSSIBLE CAUSE

Open or short circuit

Open or short circuit

Open or short circuit

Open or short circuit

Open or short circuit

Open or short circuit

Air mix door stuck

Open position signal circuit

Mode door stuck

Open position signal circuit

Open or short circuit

Vent door stuck
Refer to PAGE

22-16

22-1

8

22-20
22-22
22-24
22-2
6
22-28
22-30
22-32
INDICATOR

MODE

A/C
ON
(A/C)

OFF
(A/C)

LED on

defroster

button

A

B

C
D

E

F

G
H
I
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