Infiniti G37 Coupe. Manual - part 1242

POWER STEERING CONTROL UNIT

STC-19

< ECU DIAGNOSIS >

[WITHOUT 4WAS]

C

D

E

F

H

I

J

K

L

M

A

B

STC

N

O

P

JCGWA0047GB

STC-20

< ECU DIAGNOSIS >

[WITHOUT 4WAS]

POWER STEERING CONTROL UNIT

Fail Safe

INFOID:0000000001666282

EPS system

JCGWA0048GB

POWER STEERING CONTROL UNIT

STC-21

< ECU DIAGNOSIS >

[WITHOUT 4WAS]

C

D

E

F

H

I

J

K

L

M

A

B

STC

N

O

P

• EPS system enters the fail-safe mode (that allows the steering

force to be controlled without impairing the drive ability) if any of
the input/output values to/from EPS system (power steering con-
trol unit) deviate from the standard range.
NOTE:
The system enters the fail-safe mode if the engine speed remains
at 1,500 rpm or more for over 10 seconds while the vehicle is
stopped. This is normal.

• The fail-safe function is canceled when a vehicle speed signal of 2

km/h (1.2 MPH) or more is inputted or the key switch is turned
OFF

→

ON. EPS system restores the normal operation at that time.

JSGIA0114GB

Function

Warn-

ing lamp

DTC No.

Detection point (malfunction part)

Malfunction part and cause

Fail-safe 

function

—

—

Vehicle speed signal input

• Engine speed is 1,500 rpm or more and there is no vehicle 

speed signal input for over 10 seconds during vehicle travel.

• Vehicle speed signal has abruptly dropped from 30 km/h (19 

MPH) or more to 2 km/h (1.2 MPH) or less within 1.4 sec-
onds.

STC-22

< SYMPTOM DIAGNOSIS >

[WITHOUT 4WAS]

UNBALANCE STEERING WHEEL TURNING FORCE (TORQUE VARIATION)

SYMPTOM DIAGNOSIS

UNBALANCE STEERING WHEEL TURNING FORCE (TORQUE VARIA-
TION)

Description

INFOID:0000000001666283

• Hard steering when fully turning the steering wheel.
• Light steering when driving at a high speed.

Diagnosis Procedure

INFOID:0000000001666284

1.

CHECK SYSTEM FOR POWER SUPPLY AND GROUND

Perform trouble diagnosis for power supply and ground. Refer to 

STC-10, "Diagnosis Procedure"

.

Is the inspection result normal?

YES

>> GO TO 2.

NO

>> Repair or replace damaged parts.

2.

CHECK SYSTEM FOR VEHICLE SPEED SIGNAL

Perform trouble diagnosis for vehicle speed signal. Refer to 

STC-15, "Diagnosis Procedure"

.

Is the inspection result normal?

YES

>> GO TO 3.

NO

>> Repair or replace damaged parts.

3.

CHECK SYSTEM FOR ENGINE SPEED SIGNAL

Perform trouble diagnosis for engine speed signal. Refer to 

STC-13, "Diagnosis Procedure"

.

Is the inspection result normal?

YES

>> GO TO 4.

NO

>> Repair or replace damaged parts.

4.

CHECK SYSTEM FOR POWER STEERING SOLENOID VALVE

Perform trouble diagnosis for power steering solenoid valve. Refer to 

STC-11, "Diagnosis Procedure"

.

Is the inspection result normal?

YES

>> Perform the symptom diagnosis for the steering system. Refer to 

ST-3, "NVH Troubleshooting

Chart"

.

NO

>> Repair or replace damaged parts.