Nissan Altima L32. Manual - part 1400

POWER STEERING CONTROL UNIT

STC-19

< ECU DIAGNOSIS >

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STC

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Fail Safe

INFOID:0000000004205838

EPS system

ABGIA0012GB

STC-20

< ECU DIAGNOSIS >

POWER STEERING CONTROL UNIT

• 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 signals to/from EPS system (power steering con-

trol unit) deviate from the standard.

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.

JSGIA0142GB

Function

Warn-

ing lamp

DTC No.

Detection point (malfunction part)

Malfunction part and cause

Fail-safe 

function

—

—

Vehicle speed signal

• 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.

UNBALANCE STEERING WHEEL TURNING FORCE (TORQUE VARIATION)

STC-21

< SYMPTOM DIAGNOSIS >

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SYMPTOM DIAGNOSIS

UNBALANCE STEERING WHEEL TURNING FORCE (TORQUE VARIA-
TION)

Description

INFOID:0000000004205839

• Hard steering when fully turning the steering wheel.

• Light steering when driving at a high speed.

Diagnosis Procedure

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1.

CHECK SYSTEM FOR POWER SUPPLY AND GROUND

Perform trouble diagnosis for power supply and ground circuit. Refer to 

STC-6, "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-13, "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-10, "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-8, "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.

STC-22

< PRECAUTION >

PRECAUTIONS

PRECAUTION

PRECAUTIONS

Precautions for Supplemental Restraint System (SRS) "AIR BAG" and "SEAT BELT 
PRE-TENSIONER"

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The Supplemental Restraint System such as “AIR BAG” and “SEAT BELT PRE-TENSIONER”, used along

with a front seat belt, helps to reduce the risk or severity of injury to the driver and front passenger for certain

types of collision. This system includes seat belt switch inputs and dual stage front air bag modules. The SRS

system uses the seat belt switches to determine the front air bag deployment, and may only deploy one front

air bag, depending on the severity of a collision and whether the front occupants are belted or unbelted.

Information necessary to service the system safely is included in the SR and SB section of this Service Man-

ual.

WARNING:

• To avoid rendering the SRS inoperative, which could increase the risk of personal injury or death in

the event of a collision which would result in air bag inflation, all maintenance must be performed by

an authorized NISSAN/INFINITI dealer.

• Improper maintenance, including incorrect removal and installation of the SRS, can lead to personal

injury caused by unintentional activation of the system. For removal of Spiral Cable and Air Bag

Module, see the SR section.

• Do not use electrical test equipment on any circuit related to the SRS unless instructed to in this

Service Manual. SRS wiring harnesses can be identified by yellow and/or orange harnesses or har-

ness connectors.

Precautions Necessary for Steering Wheel Rotation after Battery Disconnect

INFOID:0000000004205842

NOTE:

• Before removing and installing any control units, first turn the push-button ignition switch to the LOCK posi-

tion, then disconnect both battery cables.

• After finishing work, confirm that all control unit connectors are connected properly, then re-connect both

battery cables.

• Always use CONSULT-III to perform self-diagnosis as a part of each function inspection after finishing work.

If a DTC is detected, perform trouble diagnosis according to self-diagnosis results.

This vehicle is equipped with a push-button ignition switch and a steering lock unit.

If the battery is disconnected or discharged, the steering wheel will lock and cannot be turned.

If turning the steering wheel is required with the battery disconnected or discharged, follow the procedure

below before starting the repair operation.

OPERATION PROCEDURE

1. Connect both battery cables.

NOTE:

Supply power using jumper cables if battery is discharged.

2. Carry the Intelligent Key or insert it to the key slot and turn the push-button ignition switch to ACC position.

(At this time, the steering lock will be released.)

3. Disconnect both battery cables. The steering lock will remain released with both battery cables discon-

nected and the steering wheel can be turned.

4. Perform the necessary repair operation.
5. When the repair work is completed, re-connect both battery cables. With the brake pedal released, turn

the push-button ignition switch from ACC position to ON position, then to LOCK position. (The steering

wheel will lock when the push-button ignition switch is turned to LOCK position.)

6. Perform self-diagnosis check of all control units using CONSULT-III.