Nissan Altima L32. Manual - part 1396

EPS SYSTEM

STC-3

< FUNCTION DIAGNOSIS >

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FUNCTION DIAGNOSIS

EPS SYSTEM

System Diagram

INFOID:0000000004205824

CONTROL DIAGRAM

System Description

INFOID:0000000004205825

• The EPS system controls the power steering solenoid valve through the power steering control unit.

• The valve driving voltage to control the power steering solenoid

valve varies 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 occurred in "2R" and "3R". This

results in a light steering force because of high pressure.

JSGIA0119GB

JSGIA0141GB

JSGIA0020GB

STC-4

< FUNCTION DIAGNOSIS >

EPS SYSTEM

During High-speed Operation

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. Oil pressure "2R" does not occur because the power steering solenoid valve is on full throttle.

4. Oil pressure "P" in the gear housing assembly includes only oil pressure occurred in "3R" and results in a

heavy steering force.

Component Parts Location

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JSGIA0021GB

ALGIA0029ZZ

EPS SYSTEM

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Component Description

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1.

Power steering control unit M59 
(view with glove box removed)

2.

Power steering solenoid valve E14

Component parts

Function

Power steering control unit

• Signals from various sensors control the driving voltage to the power steering solenoid valve.
• The power steering control unit controls the driving voltage to the power steering solenoid valve 

for maintaining the power steering assist force when the fail-safe function is activated. (The en-
gine speed signals control EPS system if any vehicle speed signal error is detected.)

Combination meter

Refer to 

STC-13, "Description"

.

ECM

Refer to 

STC-10, "Description"

.

Power steering solenoid valve

Refer to 

STC-8, "Description"

.

STC-6

< COMPONENT DIAGNOSIS >

POWER SUPPLY AND GROUND CIRCUIT

COMPONENT DIAGNOSIS

POWER SUPPLY AND GROUND CIRCUIT

Description

INFOID:0000000004205828

• EPS system functions by ignition power supply.

Diagnosis Procedure

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1.

CHECK POWER SUPPLY

1. Turn the ignition switch OFF.

2. Disconnect power steering control unit harness connector.

3. Check voltage between power steering control unit harness con-

nector M59 terminal 3 and ground.

4. Turn the ignition switch ON.

CAUTION:

Never start the engine.

5. Check voltage between power steering control unit harness con-

nector M59 terminal 3 and ground.

Is the inspection result normal?

YES

>> GO TO 2.

NO

>> Check the following. If any items are damaged, repair

or replace damaged parts.

• 10A fuses (#3) open

- Harness for short or open between ignition switch and power steering control unit harness con-

nector No. 3 terminal.

- Ignition switch.

2.

CHECK GROUND CIRCUIT

1. Turn the ignition switch OFF.

2. Check continuity between power steering control unit harness

connector M59 terminal 6 and ground.

Is the inspection result normal?

YES

>> GO TO 3.

NO

>> Repair open circuit or short to power in harness or con-

nectors.

3.

CHECK TERMINALS AND HARNESS CONNECTORS

Check power steering control unit pin terminals for damage or loose connection with harness connector.

Power steering control unit

Voltage (Approx.)

Connector

Terminal

M59

3 - Ground

0 V

AWGIA0032ZZ

Power steering control unit

Voltage (Approx.)

Connector

Terminal

M59

3 - Ground

Battery voltage

AWGIA0033ZZ

Power steering control unit

Continuity

Connector

Terminal

M59

6 - Ground

Existed

AWGIA0034ZZ