sensor ACURA NSX 1991 Service Repair Manual

Control Box
EVAPORATIVE EMISSION
(EVAP) PURGE CONTROL SOLENOID

VALVE

Troubleshooting, page 11-154

EXHAUST GAS RECIRCULATION (EGR) CONTROL SOLENOID
VALVE
Troubleshooting,

page 11-145
EXHAUST GAS RECIRCULATION (EGR)
VACUUM CONTROL VALVE

Troubleshooting, page 11-145

MANIFOLD ABSOLUTEPRESSURE (MAP) SENSOR
Troubleshooting, page 11 -58

(cont'd)

INTAKE AIR BYPASS (IAB) VACUUM TANK
INTAKE AIR BYPASS (IAB) CHECK VALVE INTAKE AIR BYPASS
(IAB) CONTROL SOLENOID

VALVE

Troubleshooting,

page 11-137ProCarManuals.com

System Description
Vacuum Connections (cont'd)
FRONT HEATED OXYGEN SENSOR (HO2S)
REAR HEATED OXYGEN SENSOR (HO2S)
MANIFOLD ABSOLUTE PRESSURE (MAP) SENSORINTAKE AIR TEMPERATURE (IAT) SENSOR
FRONT KNOCK SENSOR (KS)
REAR KNOCK SENSOR (KS) IDLE AIR CONTROL (IAC) VALVE
FAST IDLE THERMO VALVE
AIR CLEANER (ACL) FUEL INJECTORFUEL PRESSURE REGULATOR
FUEL FILTER
FUEL PUMP (FP)
FUEL TANK
THROTTLE VALVE DASHPOT CONTROL DIAPHRAGM
THROTTLE VALVE DASHPOT CHECK VALVE INTAKE AIR BYPASS (IAB) CHECK VALVE
INTAKE AIR BYPASS (IAB) VACUUM TANK
INTAKE AIR BYPASS (IAB) CONTROL SOLENOID VALVE
INTAKE AIR BYPASS (IAB) CONTROL DIAPHRAGM
FRONT THREE WAY CATALYTIC CONVERTER (TWC)
REAR THREE WAY CATALYTIC CONVERTER (TWC)
POSITIVE CRANKCASE VENTILATION (PCV) VALVE
EXHAUST GAS RECIRCULATION (EGR) VALVE
EXHAUST GAS RECIRCULATION (EGR) VALVE LIFT SENSOR
EXHAUST GAS RECIRCULATION (EGR) VACUUM CONTROL VALVE
EXHAUST GAS RECIRCULATION (EGR) CONTROL SOLENOID VALVE
EVAPORATIVE EMISSION (EVAP) CONTROL CANISTER
EVAPORATIVE EMISSION (EVAP) PURGE CONTROL SOLENOID VALVE
EVAPORATIVE EMISSION (EVAP) PURGE CONTROL DIAPHRAGM VALVE
EVAPORATIVE EMISSION (EVAP) TWO WAY VALVEProCarManuals.com

System Description
Electrical Connections

FUSES
CLOCK (7.5 A)*

ACG
(120 A)**

ACG(S) (20 A)**

IG COIL (30 A)**

No. 2 (15 A)

No. 5 (10 A)
No.
4(15
A)

No. 7
(7.5
A)
In the under-hood
fuse/relay box In the engine
compartment
fuse/relay box

CKP/CYP

SENSOR

TO A/T
GEAR

POSITION
SWITCH

NEUTRAL

SWITCH
(M/T)

AUTO A/C

CONTROL

UNIT
CLUTCH
SWITCH
(M/T)
SERVICE

CHECK

CONNECTOR

A/C

PRESSURE

SWITCH A
A/C

PRESSURE

SWITCH B FUEL PUMP

RESISTORProCarManuals.com

MAP

SENSOR

TP SENSOR
IGNITION

TIMING

ADJUSTER
EGR VALVE
LIFT SENSOR

ACCELERATOR

PEDAL ANGLE

SENSOR

FRONT

HO2S

REAR
HO2S
REAR FRONT
KS KS

TERMINAL LOCATION
(cont'd)

REAR VTEC
SOLENOID VALVE
FRONT VTEC
SOLENOID VALVE

FRONT

VTEC

PRESSURE

SWITCH

REAR

VTEC
PRESSURE

SWITCH
TACHOMETER
CONNECTOR
IGNITION COIL

ICMProCarManuals.com

System Description

System Connecors [Engine Compartment (Right Side)] (cont'd)
C132
C171

C130
C133
KNOCK SENSOR

HARNESS

C143
C173C172

C141

C139
C140
C138

C101

C137
C146
C144 C152

C151
C149
C142

ENGINE WIRE
HARNESS
C148 C136
C135
C134
ProCarManuals.com

Troubleshooting

Troubleshooting Guide
NOTE: Across each row in the chart, the systems that could be sources of a symptom are ranked in the order they should be inspected starting with . Find the symptom in the left column, read across to the most likely source, then refer
to the page listed at the top of that column. If inspection shows the system is OK, try the next most likely system , etc.
If codes other than those listed above are indicated, count the number of blinks again. If the Malfunction Indicator
Lamp is in fact blinking these codes, substitute a known-good ECM and recheck. If the indication goes away, replace
the original ECM.
If the Malfunction Indicator Lamp is on while the engine is running, jump the service check connector. If no code
is displayed (Malfunction Indicator Lamp stays on steady), the back-up system is in operation.
Substitute a known-good ECM and recheck. If the indication goes away, replace the original ECM.
USA:

Malfunction
Indicator
Lamp (MIL)
CANADA:

Check

Engine

Light

PAGE

SYSTEM

SYMTOM
MALFUNCTION INDICATOR
LAMP"

TURNS ON

MALFUNCTION
INDICATOR LAMP BLINKS
ENGINE WON'T START
DIFFICULT TO START
ENGINE WHEN COLD
WHEN COLDFAST IDLE

OUT OF SPEC

IRREGULAR

IDLING
ROUGH IDLE
WHEN WARM

RPM

TOO HIGH
WHEN WARM
RPM

TOO LOW

WHILE
WARMING UP

FREQUENT

STALLING
AFTER

WARMING UP
MISFIRE OR

ROUGH

RUNNING

POOR
PERFORM-

ANCE
FAILS

EMISSION

TEST

LOSS OF

POWER
ENGINE

CONTROL

MODULE

11-42

HEATED

OXYGEN

SENSOR

11-48, 11-50
MANIFOLD
ABSOLUTE

PRESSURE
SENSOR

11-58
CRANKSHAFT

POSITION/
CYLINDER

POSITION
SENSOR

11-64

PGM-FI

ENGINE

COOLANT

TEMPERA-
TURE

SENSOR
THROTTLE
POSITION
SENSOR
INTAKE AIR
TEMPERA-

TURE

SENSOR
BAROMET-

RIC PRES-
SURE

SENSOR
IGNITION

OUTPUT

SIGNAL
VARIABLE VALVE

TIMING & VALVE

LIFT ELECTRONIC
CONTROL SOLENOID
VALVE

6-15

11-74

11-72
11-70

11-68
11-66
ProCarManuals.com

PGM-FI
VARIABLE VALVE
TIMING & VALVE

LIFT ELECTRONIC CONTROL PRES- SURE SWITCH VEHICLE

SPEED

SENSOR IGNITION

TIMING

ADJUSTER
KNOCK

SENSOR
A/T FI

SIGNAL A
A/T Fl

SIGNAL B
IDLE AIR
CONTROL VALVE
OTHER

IDLE

CONTROLS
FUEL

INJECTOR
FUEL

METERING
OTHER

FUEL
SUPPLY INTAKE

AIR
EXHAUST

GAS

RECIRCU-
LATION

CONTROL
SYSTEM

EMISSION CONTROL

OTHER

EMISSION
CONT-

ROLS

11-141

11-145

11-127

11-104

11-116

11-54,11-56

11-107

11-84

11-88

11-82

11-82

11-80

11-78

11-76
6-17('91-'93)
IDLE CONTROL
FUEL SUPPLY
FUEL

PUMPProCarManuals.com

PGM-FI System

System Description

INPUTS
ENGINE CONTROL MODULE (ECM)

OUTPUTS

FRONT HO2S

REAR HO2S

MAP Sensor

CKP/CYP Sensor

ECT Sensor

TP Sensor

IAT Sensor

VSS

FRONT KS

REAR KS

Ignition Timing Adjuster

EGR Valve Lift Sensor

A/T Fl Signals

TCS Signals

Starter Signal

ALT FR Signal

Air Conditioning Signal

A/T Gear Position Switch Signal

Neutral Switch Signal (M/T)

Clutch Switch Signal (M/T)

VTEC Pressure Switch

Battery Voltage (IGN.1)

Fuel Pump Terminal Voltage
Fuel Injectors

PGM-FI Main Relay (Fuel Pump)

Malfunction Indicator Lamp

IAC Valve

A/C Compressor Clutch Relay

ICM

EVAP Purge Control Solenoid Valve

Fuel Pump Relay

EGR Control Solenoid Valve

IAB Control Solenoid Valve

Engine Compartment Fan Relay

VTEC Solenoid Valve

TCS Control Signals

FRONT HO2S HEATER

REAR HO2S HEATER

PGM-FI System

The PGM-FI system on this model is a sequential multiport fuel injection system.

Fuel Injector Timing and Duration

The ECM contains memories for the basic discharge durations at various engine speeds and manifold pressures. The

basic discharge duration, after being read out from the memory, is further modified by signals sent from various sensors

to obtain the final discharge duration.

Idle Air Control

Idle Air Control (IAC) Valve

When the engine is cold, the A/C compressor is on, the transmission is in gear (A/T only) or the alternator (ALT) is charg-

ing, the ECM controls current to the IAC valve to maintain correct idle speed.

Ignition Timing Control

The ECM contains memories for basic ignition timing at various engine speeds and manifold pressures. Ignition timing

is also adjusted for engine coolant temperature.

A knock control system is also used. When detonation is detected by the knock sensor (KS), the ignition timing is

retarded.

Other Control Functions

1. Starting Control

When the engine is started, the ECM provides a rich mixture by increasing fuel injector duration.

2. Fuel Pump Control

When the ignition switch is initially turned on, the ECM supplies ground to the PGM-FI main relay that supplies

current to the fuel pump for two seconds to pressurize the fuel system.

When the engine is running, the ECM supplies ground to the PGM-FI main relay that supplies current to the fuel pump.

When the engine is not running and the ignition is on, the ECM cuts ground to the PGM-FI main relay which cuts

current to the fuel pump.

Excellent engine performance is achieved through the use of VTEC (Variable Valve Timing and Valve Lift Electron-

ic Control System), intake air bypass control and discharge volume control of the fuel pump.ProCarManuals.com

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 1 58 °F (70°C) the ECM supplies a ground to the EVAP purge control

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

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 hight 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 in, the ECM supplies ground for the MIL for two seconds

to check the MIL bulb condition.ProCarManuals.com

(From page 11 -44)
Inspect the IG COIL (30 A) fuse

in the engine compartment

fuse/relay box.
Is the fuse OK?

Turn the ignition switch ON.
Disconnect the 3P connector of
each sensor one at a time: MAP sensor

EGR
valve
lift
sensor
Accelerator pedal angle sensor
Does the MIL remain ON?
Connect the service check con-

nector terminals with a jumper

wire.
Disconnect the 3P connector of

each sensor one at a time:
TP sensor
Ignition timing adjuster

Does the MIL indicate
code 7 or 18?

Turn the ignition switch OFF.
Remove the jumper wire from the
service check connector.
Connect the test harness.

Disconnect the "D" connector

from the ECM only, not the engine

wire harness (see page 11-37).

Check for continuity between

body ground and the following

terminals: D19, D20.

(To page 11-46) Replace the fuse.
Substitute a known-good ECM
and recheck. If symptom/indica-
tion goes away, replace the origi-
nal
ECM.
Replace the sensor that caused
the light to go out upon its discon- nection.
Replace the TP sensor or ignition
timing adjuster. (From page 11-44)

Turn the ignition switch
OFF.

Disconnect "A" con-
nector from the ECM.

Turn the ignition switch

ON.
Is the MIL on?

Repair short to body
ground in BLU wire be-

tween the ECM (A13)
and
MIL.

Continuity?

(cont'd)ProCarManuals.com