Infiniti G37 Coupe. Manual - part 1246

4WAS SYSTEM

STC-35

< FUNCTION DIAGNOSIS >

[WITH 4WAS]

C

D

E

F

H

I

J

K

L

M

A

B

STC

N

O

P

• The lock structure (holder) absorbs force and applies the lock when applying strong force to 4WAS front

actuator.

CAUTION:

Replace 4WAS front actuator when the system breaks down due to the excessive external force
(rotating direction) applied to 4WAS front actuator.

4WAS REAR ACTUATOR

• It is driven by 4WAS rear motor.
• The irreversible efficiency performance hypoid gear secure the toe-stiffness of rear wheels against the road

external force and keep the steering angle when system is malfunction.

• The power from the pinion gear (motor side) is transmitted, but the pinion gear does not rotate as caused by

the gear mechanical characteristics (teeth angle) even though the ring gear (tire side) starts to rotate.

Component Parts Location

INFOID:0000000001666298

1.

Steering angle sensor

2.

4WAS warning lamp

3.

4WAS front control unit

4.

4WAS front actuator

5.

4WAS rear motor

6.

4WAS rear actuator

7.

Rear wheel steering angle sensor

8.

4WAS main control unit

9.

4WAS rear motor relay

10
.

Noise suppressor

JSGIA0236ZZ

STC-36

< FUNCTION DIAGNOSIS >

[WITH 4WAS]

4WAS SYSTEM

Component Description

INFOID:0000000001666299

*: Communication line between 4WAS front control unit and 4WAS main control unit

A.

Combination switch

B.

Inside combination meter

C.

Inside the instrument driver lower 
panel

D.

4WAS rear actuator assembly

E.

Inside the rear wheel house finisher 
(left)

Component parts

Reference/Function

4WAS front control unit

STC-55, "Description"

4WAS front actuator

The front wheel steering angle is activated.

Front wheel steering angle sensor

The front wheel steering angle increased/decreased degree is detected. It is output to 4WAS 
front control unit.

4WAS front motor

The front wheel steering angle increased/decreased degree is activated.

4WAS front lock solenoid valve

Secure the inside of 4WAS front actuator temporarily. (It operates when performing active 
test with fail-safe function and CONSULT-III.)

Steering angle sensor

STC-112, "Description"

4WAS main control unit

STC-87, "Description"

4WAS rear actuator

The rear wheel steering angle is activated.

Rear wheel steering angle sensor

The rear wheel steering angle increased/decreased degree is detected. It is output to 4WAS 
main control unit.

4WAS rear motor

4WAS rear actuator is activated.

ABS actuator and electronic unit (con-
trol unit)

STC-110, "Description"

ECM

STC-115, "Description"

Combination meter

It mainly transmits the following signals from 4WAS main control unit with CAN communica-
tion.
• 4WAS warning lamp signal

Power steering solenoid valve

The power steering oil pressure in the gear housing assembly is controlled.

Stop lamp switch

The stop lamp switch condition is detected.

EPS SYSTEM

STC-37

< FUNCTION DIAGNOSIS >

[WITH 4WAS]

C

D

E

F

H

I

J

K

L

M

A

B

STC

N

O

P

EPS SYSTEM

System Diagram

INFOID:0000000001666300

System Description

INFOID:0000000001666301

DESCRIPTION

• The EPS system controls the power steering solenoid valve with 4WAS main control unit.
• The power steering solenoid valve control changes the power

steering solenoid valve activation voltage according to the vehicle
speed.

OPERATION PRINCIPLE

During Parking (When Turning The Steering Wheel To The Right.)

1.

Power steering solenoid valve is closed while a vehicle is stopped.

2.

Pinion “1R”, “2R” and “3R” are closed depending on steering torque of steering wheel.

3.

Oil pressure “P” in the gear housing assembly is the sum of oil pressures occurring in “2R” and “3R”. This
results in a light steering force because of high pressure.

During High-speed Operation

JSGIA0259GB

JSGIA0053GB

JSGIA0012GB

STC-38

< FUNCTION DIAGNOSIS >

[WITH 4WAS]

EPS SYSTEM

1.

Power steering solenoid valve is opened during high-speed operation.

2.

Pinion “1R”, “2R” and “3R” are closed depending on steering torque of steering wheel.

3.

“2R” is bypassed to the return port by the EPS solenoid valve.

4.

Oil pressure “P” in the gear housing assembly includes only oil pressure occurring in “3R” and results in a
heavy steering force.

Component Parts Location

INFOID:0000000001666302

Component Description

INFOID:0000000001666303

JSGIA0013GB

1.

Power steering solenoid valve

2.

4WAS main control unit

A.

Steering gear assembly

B.

Inside the rear wheel hose finisher 
(left)

:Vehicle front

JSGIA0237ZZ

Component parts

Function

4WAS main control unit

• The power steering solenoid valve activation voltage is controlled by each sensor signal.
• The power steering solenoid valve activation voltage is controlled by 4WAS main control 

unit for maintaining the power steering force in the fail-safe mode. (EPS system is con-
trolled by the engine speed signal if the vehicle speed signal error is detected.)

ABS actuator and electric unit (control 
unit)

It mainly transmits the following signals to 4WAS main control unit with CAN communication.
• Vehicle speed signal

ECM

It mainly transmits the following signals to 4WAS main control unit with CAN communication.
• Engine speed signal

Power steering solenoid valve

The power steering oil pressure in the gear housing assembly is controlled.