Nissan Pathfinder. Manual - part 1122

COMPONENT PARTS

STC-5

< SYSTEM DESCRIPTION >

C

D

E

F

H

I

J

K

L

M

A

B

STC

N

O

P

Power Steering Oil Pump Assembly

INFOID:0000000009177125

The power steering oil pump assembly is primarily composed of the

reservoir tank (1), power steering oil pump (2), power steering motor

(3), and power steering control module (4).

RESERVOIR TANK

Fluid is filled from the reservoir tank.

POWER STEERING OIL PUMP

The power steering oil pump is driven by the power steering motor and generates hydraulic oil pressure in the

system.

POWER STEERING MOTOR

The power steering motor is controlled by the power steering control module and drives the power steering oil

pump.

POWER STEERING CONTROL MODULE

By receiving steering angle sensor signal and vehicle speed signal, the power steering control module calcu-

lates hydraulic pressure of the hydraulic pump electric power steering system according to the driving condi-

tions. The power steering control module controls the power steering motor.

JSGIA0914ZZ

STC-6

< SYSTEM DESCRIPTION >

SYSTEM

SYSTEM

HYDRAULIC PUMP ELECTRIC POWER STEERING SYSTEM
HYDRAULIC PUMP ELECTRIC POWER STEERING SYSTEM : System Description

INFOID:0000000009177126

• The system is composed primarily of the power steering oil pump assembly (power steering control module,

power steering motor, power steering oil pump, and reservoir tank), hydraulic pipes, and steering gear

assembly.

• The power steering control module controls the speed of the power steering motor according to the vehicle

speed and steering angle speed. By changing the power steering oil pump flow, the power steering control

module controls the steering assist force.

• According to the power steering motor control, the system hydraulic pressure is transmitted from the power

steering motor to power steering oil pump. The power steering oil pump is driven by the system hydraulic

pressure.

• After engine start, the hydraulic pump electric power steering system performs control.

• When a malfunction occurs in the system, the fail-safe function stops the hydraulic pump electric power

steering system (manual steering state) or restricts its operation (certain steering assist force). Refer to 

STC-

8, "HYDRAULIC PUMP ELECTRIC POWER STEERING SYSTEM : Fail-safe"

.

• When the power steering function is used continuously in an extreme manner, the protective function

reduces the output to the power steering motor. Refer to 

STC-9, "HYDRAULIC PUMP ELECTRIC POWER

STEERING SYSTEM : Protection Function"

.

SYSTEM DIAGRAM

INPUT/OUTPUT SIGNAL

Communicates the signal from each control unit via CAN communication.

OPERATION CHARACTERISTICS

ALGIA0127GB

Control unit

Signal status

ECM

Transmits engine status signal to power steering control module via CAN communication.

Steering angle sensor

Transmits steering angle sensor signal  to power steering control module via CAN commu-
nication.

Combination meter

Transmits vehicle speed signal to power steering control module via CAN communication.

Receives hydraulic pump electric power steering warning lamp signal from power steering 
control module via CAN communication.

SYSTEM

STC-7

< SYSTEM DESCRIPTION >

C

D

E

F

H

I

J

K

L

M

A

B

STC

N

O

P

When the steering angle speed is high or the vehicle speed is low,

force is generated by increasing discharge amount from the power

steering oil pump and by raising system hydraulic pressure.

OPERATION PRINCIPLE

When Steering Wheel is in the Neutral Position

Because the hydraulic routes open at the power steering pump, gear housing right side, gear housing left side,

and reservoir tank, the hydraulic pressure applied to the right side and left side of the gear housing is equal

and no steering assist force is generated. 

When Steering Wheel is Rotated to the Right

The hydraulic routes open from power steering pump to gear housing right side and from gear housing left

side to reservoir tank, providing left direction assist force to the rack.

JSGIA0916GB

JSGIA0918GB

JSGIA0919GB

STC-8

< SYSTEM DESCRIPTION >

SYSTEM

When Steering Wheel is Rotated to the Left

The hydraulic routes open from power steering pump to gear housing left side and from gear housing right

side to reservoir tank, providing right direction assist force to the rack.

CONDITIONS FOR HYDRAULIC PUMP ELECTRIC POWER STEERING WARNING LAMP ON

• When the hydraulic pump electric power steering system is operating and steering assist force is being gen-

erated, the hydraulic pump electric power steering warning lamp is OFF.

• When the hydraulic pump electric power steering system is stopped by the fail-safe or protective function

and steering assist force is not being generated, the hydraulic pump electric power steering warning lamp

turns ON to inform the driver that the system is in the manual steering state.

NOTE:

When the hydraulic pump electric power steering system warning lamp turns ON according to the protection

system, the cause is internal high temperature state of the hydraulic pump electric power steering system.

By stopping the engine, internal temperature of the system decreases. After starting the engine, the system

returns to the normal state and the hydraulic pump electric power steering system warning lamp turns OFF.

(The system is not malfunctioning.) For information about the protective function, refer to 

STC-9, "HYDRAU-

LIC PUMP ELECTRIC POWER STEERING SYSTEM : Protection Function"

.

• When the ignition switch is turned ON, this lamp turns ON for lamp check (system check). When the system

is operating normally, the lamp turns OFF after the engine starts.

HYDRAULIC PUMP ELECTRIC POWER STEERING SYSTEM : Fail-safe

INFOID:0000000009177127

When an error occurs in the hydraulic pump electric power steering system, fail-safe brings the system to a

halt (manual steering) or restricted (constant steering assist level) state. When the system is in a halt state,

fail-safe turns ON the hydraulic pump electric power steering warning lamp to warn the driver that the hydrau-

lic pump electric power steering system is in the manual steering state.

JSGIA0917GB

Condition

Hydraulic pump electric power steering warning lamp

Ignition switch ON. (Lamp check)

ON

After engine start (steering assist force is generated)

OFF

When steering assist is stopped

ON

DTC

Fail-safe condition

C1143

Certain steering assist force

C1601

Manual steering state

C1606

Manual steering state

C1607

Certain steering assist force