check engine light ACURA NSX 1997 Service Repair Manual

Pulsed Secondary Air Injection System Description

The air pump system is designed to advance the activation of the catalyst and to reduce the hydrocarbons (HC), carbon

monoxide (CO), and oxides of nitrogen (NOx) in the exhaust gas.

The system operates after the engine starts under the following conditions:

• The engine coolant temperature is between 0°C and 70°C (32°F and 158°F).

• The difference in engine coolant temperature is more than 20°C (36°F) between the time when the engine is started and

when the engine is stopped in the previous driving cycle.

AIR CONTROL

SOLENOID VALVE

AIR CONTROL

VALVE

WHT

AIR PUMP

RELAY
From

No. 5 BACK-UP LIGHTS

ALTERNATOR

TURN SIGNALS

(15 A) FUSE

From

AIR PUMP

(60 A) FUSE

AIR CONTROL VALVE

VACUUM TANK

AIR CONTROL VALVE

CHECK VALVE

When the engine is started, the air pump runs and sends fresh air to the air control valve. The air control valve allows the

fresh air to flow to the exhaust ports when its diaphragm is pulled by engine vacuum. It gets engine vacuum from the air

control solenoid, which is activated by the ECM. Once the fresh air flows into the exhaust ports near the exhaust valves, it

reacts with the exhaust gases, raising exhaust gas temperatures. This promotes faster warm-up of the catalytic converter.

The system operates for a maximum of 60 seconds, but the running time shortens in relation to the engine coolant tem-

perature and the intake air temperature. When the system is not operating, the air control solenoid and the air control

valve are closed to prevent exhaust gases from entering the system.
AIR PUMP

ELECTRICAL

CURRENT

SENSORProCarManuals.com

Camshafts

Installation (cont'd)

17. Apply liquid gasket to the head cover gasket at the

eight corners of the recesses.

NOTE:

• Use liquid gasket, Part No. 08718 - 0001 or 08718

- 0003.

• Check that the mating surfaces are clean and dry

before applying liquid gasket.

• Do not install the parts if five minutes or more

have elapsed since applying liquid gasket. Instead,

reapply liquid gasket after removing old residue.

• After assembly, wait at least 20 minutes before

filling the engine with oil.

Apply liquid gasket to

the shaded areas.

18. When installing the cylinder head cover, hold the

head cover gasket in the groove by placing your fin-

gers on the camshaft contacting surfaces (top of the

semicircles).

Once the cylinder head cover is on the camshaft

holder, slide the cover slightly back and forth to

seat the head cover gasket.

NOTE:

• Before installing the cylinder head cover, clean

the cylinder head contacting surfaces with a

shop towel.

• Do not touch the parts where liquid gasket was

applied.

• Replace the washer when damaged or deterio-

rated.

CYLINDER

HEAD COVER
WASHER

6 x 1.0 mm

12 N-m (1.2 kgf-m,

8.7 Ibf-ft)
19. Tighten the nuts in two or three steps. In the final step,

tighten all nuts, in sequence, to 12 N-m (1.2 kgf-m,

8.7 Ibf-ft).

NOTE: After assembly, wait at least 20 minutes

before filling the engine with oil.

20. After installation, check that all tubes, hoses and

connectors are installed correctly.

NOTE: After installation, fill the engine with oil up to

the specified level, run the engine for more than three

minutes, then check for oil leakage.ProCarManuals.com

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 1,500 rpm.

Fuel cut-off action also takes place when engine speed exceeds 8,300 rpm, regardless of the position of the throttle

valve, to protect the engine from over-revving.

4. A/C Compressor Clutch Relay

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

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

5. Evaporative Emission (EVAP) Purge Control Solenoid Valve

When the engine coolant temperature is below 153°F (67°C), the ECM controls the EVAP purge control solenoid valve

which cuts vacuum to the EVAP purge control canister diaphragm.

6. Intake Air Bypass (IAB) Control Solenoid Valve

When the engine speed is below 4,800 rpm, the IAB control solenoid valve is activated by a signal from the ECM. Intake

air then flows through the smaller chamber, and high torque is delivered. To increase air flow at engine speeds higher

than 4,800 rpm, the solenoid valve is deactivated by the ECM, and the intake air flows through the larger chamber.

7. Exhaust Gas Recirculation (EGR) Control Solenoid Valve

When the EGR is required for control of oxides of nitrogen (NOx) emissions, the ECM supplies ground to 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 ECM ignores that signal and assumes a pre-programmed

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

2. Back-up Function

When an abnormality occurs in the ECM 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 ECM lights the MIL and stores the diagnostic trouble code

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

check the MIL bulb condition.

4. Two Trip Detection Method

To prevent false indications, the Two Trip Detection Method is used for the H02S, fuel metering-related, idle control

system, ECT sensor, EGR system self-diagnostic functions and EVAP control system. When an abnormality occurs,

the ECM stores it in its memory. When the same abnormality recurs after the ignition switch is turned OFF and ON (II)

again, the ECM 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.

5. Two (or three) Driving Cycle Detection Method

A "Driving Cycle" consists of starting the engine, beginning closed loop operation, and stopping the engine. If misfir-

ing that increases emissions or EVAP control system malfunction is detected during two consecutive driving cycles,

or TWC deterioration is detected during three consecutive driving cycles, the ECM turns the MIL on.

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

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

CLOSED: LOW ENGINE SPEED

IAB CONTROL

SOLENOID

VALVE

To No. 5 BACK-UP LIGHTS

ALTERNATOR TURN SIGNALS

(15 A) FUSE

IAB

CONTROL

DIAPHRAGM

•IAB

CONTROL

VALVE
IAB

CHECK

VALVE

IAB

VACUUM

TANK
VARIOUS

SENSORSProCarManuals.com

Emission Control System

Positive Crankcase Ventilation (PCV) System

Description

The Positive Crankcase Ventilation (PCV) system is

designed to prevent blow-by gas from escaping to the

atmosphere. The PCV valve contains a spring-loaded

plunger. When the engine starts, the plunger in the PCV

valve is lifted in proportion to intake manifold vacuum

and the blow-by gas is drawn directly into the intake

manifold.

PCV HOSE
INTAKE MANIFOLD

PCV VALVE
Inspection

1. Check the PCV hoses and connections for leaks and

clogging.

BREATHER

PIPE

PCV VALVE

PCV HOSE

2. At idle, make sure there is a clicking sound from the

PCV valve when the hose between PCV valve and

intake manifold in lightly pinched with your fingers

or pliers.

Gently pinch here

If there is no clicking sound, check the PCV valve

grommet for cracks or damage. If the grommet is

OK, replace the PCV valve and recheck.
BLOW-BY VAPOR

FRESH AIR
BREATHER PIPEProCarManuals.com

Troubleshooting Precautions

EPS Indicator Light

Under normal conditions, the EPS indicator light in the gauge assembly comes on when the ignition switch is turned to

the ON (II) position, then goes off after the engine is started. This indicates that the bulb and its circuits are operating cor-

rectly. If there is any trouble in the system, the EPS indicator light turns on during driving, and the power steering assist is

turned off. When the EPS indicator light comes on, the control unit memorizes the DTC. In this case, the control unit does

not activate the EPS system after the engine starts again but it keeps the EPS indicator light on.

Diagnostic Trouble Code (DTC)

• The lowest DTC is indicated first.

• The DTCs continue blinking until the ignition switch is turned off.

• The DTCs are erased from the control unit when the EPS control unit VBU power supply or connector is disconnected.

• The EPS system can be reset and the control unit's memory can be erased by disconnecting the CLOCK (7.5 A) fuse for

more than ten seconds.

Self-diagnosis:

The CPU (central processing unit) controls the following when it detects a problem during self-diagnosis:

1. Turns the EPS indicator light ON to alert the driver.

2. Power assist stops, and normal manual steering operation resumes (except DTC 33).

3. The EPS control unit memorizes the diagnostic trouble code (DTC).

4. After the DTC is stored in the control unit, the CPU stops self-diagnosis.

Troubleshooting:

• Before starting the troubleshooting, clear the DTC by disconnecting the CLOCK (7.5 A) fuse for ten seconds or more,

and test-drive the car. Check that the symptom of the trouble appears again, and then troubleshoot.

• When both EPS indicator light and A/T "D" indicator light come on, perform the A/T troubleshooting first.

• When the customer's reported problem cannot be verified in the car, ask the customer about the conditions when the

EPS indicator light came ON, then test-drive the car under those conditions, if possible. If the EPS indicator light does

not come ON during the test, check for loose connections or poor contacts at the connectors by wiggling the harness,

etc.

• The connector terminal numbers are viewed from the wire side for the female terminals and from the terminal side for

the male terminals.

• After the repair, test-drive the car and check that the EPS indicator light does not come ON again during the test. (Refer

to the Symptom-to-System Chart for diagnostic period.)ProCarManuals.com

Tests
Brake Booster

Functional Test

1. With the engine stopped, depress the brake pedal

several times to deplete the vacuum reservoir, then

depress the pedal hard and hold it for 15 seconds. If

the pedal sinks, either the master cylinder is

bypassing internally, or the brake system (master

cylinder, lines, modulator, proportioning valve, or

calipers) is leaking.

2. Start the engine with the pedal depressed. If the

pedal sinks slightly, the vacuum booster is operat-

ing normally, if the pedal height does not vary, the

booster or check valve is faulty.

3. With the engine running, depress the brake pedal

lightly. Apply just enough pressure to hold back

automatic transmission creep. If the brake pedal

sinks more than 10 mm (3/8 in.) in three minutes,

the master cylinder is faulty. A slight change in

pedal height when the A/C compressor cycles on

and off if normal. (The A/C compressor load

changes the vacuum available to the booster.)

Leak Test

1. Depress the brake pedal with the engine running,

then stop the engine. If the pedal height does not

vary while depressed for 30 seconds, the vacuum

booster is OK. If the pedal rises, the booster is

faulty.

2. With the engine stopped, depress the brake pedal

several times using normal pressure. When the

pedal is first depressed, it should be low. On con-

secutive applications, the pedal height should grad-

ually rise. If the pedal position does not vary, check

the booster check valve.
Booster Check Valve Test

1. Disconnect the brake booster vacuum hose at the

booster or at the booster side of the valve.

2. Start the engine and let it idle. There should be vac-

uum. If no vacuum is available, the check valve is

not working properly. Replace the check valve and

retest.ProCarManuals.com

ABS Control Unit

The ABS control unit consists of a main function section, which controls the operation of anti-lock brake system, and sub-

function, which controls the pump motor and "self-diagnosis."

1. Main Function

The main function section of the ABS control unit performs calculations on the basis of the signals from each wheel

sensor and controls the operation of the anti-lock brake system by putting into action the solenoid valves in the modu-

lator unit for each front and rear brake.

2. Sub-Function

The sub-function section gives driving signals to the pump motor and also gives "self-diagnosis" signals, necessary for

backing up the anti-lock brake system.

Self-Diagnostic Function

Since the anti-lock brake system modulates the braking pressure when a wheel is about to lock, regardless of the driver's

intention, the system operation and the braking power will be impaired if there is a malfunction in the system. To prevent

this possibility, at speeds above 6 mph (10 km/h), the self-diagnosis function monitors the main system functions. When

an abnormality is detected, the ABS indicator light comes on.

There is also a check mode of the self-diagnosis system itself: when the ignition switch is first turned on, the ABS indicator

light comes on and stays on for a few seconds after the engine starts, to signify that the self-diagnosis system is functional.

Fail-Safe Function

If an abnormality is detected, the ABS control unit turns off the fail-safe relays and motor relay. In this condition, the anti-

lock brake system is prevented from functioning, yet the basic brake system continues to operate normally.

The ABS Indicator Light Comes On

1. When the fluid pressure pump runs more than 120 seconds.

2. When the parking brake is applied for more than 30 seconds while the vehicle is being driven.

3. When the rear wheel(s) is (are) locked more than a specified time.

4. When the wheel rotation signal is not transmitted due to faulty wire or sensor.

5. When the operation time of the solenoid valve(s) exceeds a predetermined valve, and the ABS control unit finds an

open in the solenoid circuit.

6. When the output signals from both main functions in the ABS control unit are not transmitted to the solenoid valve(s).

(cont'd)ProCarManuals.com

NOTE:

• The TCS control unit has three memory registers. When a problem occurs, the control unit stores the Diagnostic

Trouble Code (DTC) in the first memory register. If another problem occurs, or the same problem occurs again, the con-

trol unit moves the first code to the next memory register and stores the second code in the first register. If there's a

third problem occurrence, the two existing code are moved up one register and the third code is stored in the first reg-

ister. If problems continue to occur, the oldest code is moved out of the last register and lost, and the most recent code

is stored in the first register.

• The TCS indicator light will not come on again after the engine starts unless another problem occurence is detected.

However, there will still be a code stored in the control unit's memory.

• After the repair is completed, disconnect the SCS service connector from the Service Check connector, and remove the

CLOCK (7.5 A) fuse from the under-hood fuse/relay box for at least three seconds to erase the control unit's memory.

• The control unit's memory is erased if the connector is disconnected from the control unit or if the control unit is

removed from the car.ProCarManuals.com

Rear Window Defogger Timer System:

Terminal Test condition
Test: Desired result
Possible cause if result is not obtained

A8

A9

A5

WHT/RED

A10
Under all conditions

Under all conditions

Ignition switch ON (II)

Defogger switch

pushed

Ignition switch ON (II)
Check for continuity to ground:

There should be continuity.

Check for voltage to ground:

There should be battery voltage.

Check for voltage to ground:

There should be battery voltage.

Check for continuity to ground:

There should be continuity as the

switch is pushed.

Attach to ground: The rear window

defogger should work and the

defogger switch indicator light

should come on.
• Poor ground (G401, G402, G403)

• An open in the wire

• Blown No. 34 (15 A) fuse

• An open in the wire

• Blown No. 5 (15 A) fuse

• An open in the wire

• Faulty defogger switch

• Poor ground (G401, G402, G403)

• An open in the wire

• Blown No. 4 (15 A) fuse

• Faulty defogger relay

• Blown bulb

• An open in the wire

Oil Pressure Indicator System:

Terminal Test condition
Test: Desired result
Possible cause if result is not obtained

A8

A9

A5 '

WHT/BLU2

YEL/RED
Under all conditions

Under all conditions

Ignition switch ON (II)

Engine running

Ignition switch OFF

Ignition switch ON (II)

Start the engine.
Check for continuity to ground:

There should be continuity.

Check for voltage to ground:

There should be battery voltage.

Check for voltage to ground:

There should be battery voltage.

Check for voltage to ground:

There should be battery voltage.

Check for continuity to ground:

There should be continuity.

Check indicator light operation.

If the light does not come on, attach

the YEL/RED terminal to ground: The

light should come on as the ignition

switch is turned ON (II).

Check for voltage to ground:

There should be battery voltage.
• Poor ground (G401, G402, G403)

• An open in the wire

• Blown No. 34 (15 A) fuse

• An open in the wire

• Blown No. 5 (15 A) fuse

• An open in the wire

• Faulty charging system

• An open in the wire

• Faulty engine oil pressure switch

• An open in the wire

• Blown bulb

• An open in the wire

• Insufficient oil

• Improper lubrication

• Faulty engine oil pressure switch

(cont'd)ProCarManuals.com