Nissan Silvia. Manual — part 162

Wiring Diagram

=NMEC0741

TEC807

GI

MA

EM

LC

FE

CL

MT

AT

PD

AX

SU

BR

ST

RS

BT

HA

SC

EL

IDX

VEHICLE SPEED SENSOR (VSS)

Wiring Diagram

EC-163

Diagnostic Procedure

NMEC0742

1

INSPECTION START

Do you have CONSULT-II?

Yes or No

Yes

©

GO TO 2.

No

©

GO TO 3.

2

CHECK OVERALL FUNCTION

With CONSULT-II

1. Turn ignition switch “OFF”.
2. Lift up the vehicle.
3. Start engine and let it idle.
4. Select “VHCL SPEED SE” in “DATA MONITOR” mode with CONSULT-II.
5. Check “VHCL SPEED SE” indication when rotating wheels with suitable gear position.

SEC421C

OK or NG

OK

©

INSPECTION END

NG

©

GO TO 4.

3

CHECK OVERALL FUNCTION

Without CONSULT-II

1. Turn ignition switch “OFF”.
2. Lift up the vehicle.
3. Start engine and let it idle.
4. Read the voltage signal between ECM terminal 32 and ground with an oscilloscope.
5. Verify that the oscilloscope screen shows a signal wave as shown below under the following conditions.

SEC422C

OK or NG

OK

©

INSPECTION END

NG

©

GO TO 4.

VEHICLE SPEED SENSOR (VSS)

Diagnostic Procedure

EC-164

4

CHECK VEHICLE SPEED SENSOR INPUT SIGNAL CIRCUIT FOR OPEN AND SHORT

1. Turn ignition switch “OFF”.
2. Disconnect ECM harness connector and combination meter harness connector.
3. Check harness continuity between ECM terminal 32 and combination meter terminal 31.

Refer to Wiring Diagram.

Continuity should exist.

4. Also check harness for short to ground and short to power.

OK or NG

OK

©

GO TO 6.

NG

©

GO TO 5.

5

DETECT MALFUNCTIONING PART

Check the following.

I

Harness connectors F4, M60

I

Harness for open or short between ECM and combination meter

©

Repair open circuit or short to ground or short to power in harness or connectors.

6

CHECK SPEEDOMETER FUNCTION

Make sure that speedometer functions properly.

OK or NG

OK

©

GO TO 8.

NG

©

GO TO 7.

7

CHECK SPEEDOMETER CIRCUIT FOR OPEN AND SHORT

Check the following.

I

Harness connectors F4, M60

I

Harness for open or short between combination meter and ABS control unit

OK or NG

OK

©

Check combination meter and vehicle speed sensor. Refer to EL section.

NG

©

Repair open circuit or short to ground or short to power in harness or connectors.

8

CHECK INTERMITTENT INCIDENT

Refer to “TROUBLE DIAGNOSIS FOR INTERMITTENT INCIDENT”, EC-82.

©

INSPECTION END

GI

MA

EM

LC

FE

CL

MT

AT

PD

AX

SU

BR

ST

RS

BT

HA

SC

EL

IDX

VEHICLE SPEED SENSOR (VSS)

Diagnostic Procedure (Cont’d)

EC-165

Description

NMEC0743

SYSTEM DESCRIPTION

NMEC0743S01

Sensor

Input Signal to ECM

ECM func-

tion

Actuator

Camshaft position sensor

Engine speed

Idle air
control

IACV-AAC valve

Mass air flow sensor

Amount of intake air

Engine coolant temperature sensor

Engine coolant temperature

Ignition switch

Start signal

Throttle position sensor

Throttle position

Park/Neutral position switch

Park/Neutral position

Air conditioner switch

Air conditioner operation

Power steering oil pressure switch

Power steering load signal

Battery

Battery voltage

Vehicle speed sensor

Vehicle speed

This system automatically controls engine idle speed to a specified
level. Idle speed is controlled through fine adjustment of the
amount of air which bypasses the throttle valve via IACV-AAC
valve. The IACV-AAC valve repeats ON/OFF operation according
to the signal sent from the ECM. The camshaft position sensor
detects the actual engine speed and sends a signal to the ECM.
The ECM then controls the ON/OFF time of the IACV-AAC valve
so that engine speed coincides with the target value memorized in
ECM. The target engine speed is the lowest speed at which the
engine can operate steadily. The optimum value stored in the ECM
is determined by taking into consideration various engine
conditions, such as during warm up, deceleration, and engine load
(air conditioner and power steering).

SEF040E

COMPONENT DESCRIPTION

NMEC0743S02

IACV-AAC Valve

NMEC0743S0201

The IACV-AAC valve is moved by ON/OFF pulses from the ECM.
The longer the ON pulse, the greater the amount of air that will flow
through the valve. The more air that flows through the valve, the
higher the idle speed.

CONSULT-II Reference Value in Data Monitor
Mode

NMEC0744

Specification data are reference values.

MONITOR ITEM

CONDITION

SPECIFICATION

IACV-AAC/V

I

Engine: After warming up

I

Air conditioner switch: “OFF”

I

Shift lever: “N”

I

No-load

Idle

20 - 40%

2,000 rpm

—

IDLE AIR CONTROL VALVE (IACV) — AUXILIARY AIR CONTROL (AAC) VALVE

Description

EC-166