Nissan Leaf. Manual - part 1140

PRECAUTIONS

STC-5

< PRECAUTION >

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- Check connection conditions of each connector are proper.

- Before connecting or disconnecting the EPS control unit harness

connector, turn power switch “OFF” and disconnect 12V battery

ground cable. Because battery voltage is applied to EPS control

unit even if power switch is turned “OFF”. Refer to 

STC-4, "Precau-

tion for Removing 12V Battery"

.

- When connecting or disconnecting pin connectors into or from

EPS control unit, take care not to damage pin terminals (bend or

break).

- When connecting pin connectors, make sure that there are no

bends or breaks on EPS control unit pin terminal.

• During quick steering, rasping noise may be heard from around the

steering wheel. This is not a malfunction. The noise is an operating

noise of the EPS system under normal conditions. If the rasping

noise occurs during slow steering, this may not be an operating

noise of the system. In this case, it is necessary to find out the

location of the noise and repair, if necessary.

SEF289H

SEF291H

STC-6

< SYSTEM DESCRIPTION >

COMPONENT PARTS

SYSTEM DESCRIPTION

COMPONENT PARTS

Component Parts Location

INFOID:0000000010119179

A.

Steering column assembly

No.

Component

Function

1.

VCM (Vehicle Control Module)

• Transmits mainly the following signals to EPS control unit via CAN communication.
- Power steering start activation request signal

Refer to 

EVC-15, "Component Parts Location"

 for detailed installation location.

2.

ABS actuator and electric unit (con-
trol unit)

• Transmits mainly the following signal to EPS control unit via CAN communication.
- Vehicle speed signal

Refer to 

BRC-10, "Component Parts Location"

 for detailed installation location.

3.

Combination meter

• Transmits mainly the following signal to EPS control unit via CAN communication.
- Vehicle speed signal

Refer to 

MWI-6, "METER SYSTEM : Component Parts Location"

 for detailed instal-

lation location.

• Turns ON the EPS warning lamp according to the signal from EPS control unit via 

CAN communication.

4.

EPS warning lamp

STC-8, "EPS SYSTEM : System Description"

5.

EPS motor

STC-7, "EPS Motor, Torque Sensor, Reduction Gear"

6.

EPS control unit

STC-7, "EPS Control Unit"

7.

Reduction gear

STC-7, "EPS Motor, Torque Sensor, Reduction Gear"

8.

Torque sensor

STC-7, "EPS Motor, Torque Sensor, Reduction Gear"

JSGIA0847GB

COMPONENT PARTS

STC-7

< SYSTEM DESCRIPTION >

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EPS Control Unit

INFOID:0000000010119180

• EPS control unit (1) is installed to steering column assembly.

• EPS control unit performs an arithmetical operation on data, such

as steering wheel turning force (sensor signal) from the torque

sensor, vehicle speed signal, etc. Then it generates an optimum

assist torque signal to the EPS motor according to the driving con-

dition.

• EPS control unit decreases the output signal to EPS motor while

extremely using the power steering function (e.g., full steering)

consecutively for protecting EPS motor and EPS control unit

(Overload protection control).

EPS Motor, Torque Sensor, Reduction Gear

INFOID:0000000010119181

EPS motor (1), torque sensor (2) and reduction gear (3) are installed

to steering column assembly.

EPS MOTOR

EPS motor provides the assist torque by the control signal from EPS control unit.

TORQUE SENSOR

Torque sensor detects the steering torque, and transmits the signal to EPS control unit.

REDUCTION GEAR

Reduction gear increases the assist torque provided from EPS motor with worm gears, and outputs to the col-

umn shaft.

JSGIA0852ZZ

JSGIA0853ZZ

STC-8

< SYSTEM DESCRIPTION >

SYSTEM

SYSTEM

EPS SYSTEM
EPS SYSTEM : System Description

INFOID:0000000010119182

SYSTEM DIAGRAM

DESCRIPTION

• EPS control unit performs an arithmetical operation on data, such

as steering wheel turning force (sensor signal) from the torque

sensor, vehicle speed signal, etc. Then it generates an optimum

assist torque signal to the EPS motor according to the driving con-

dition.

• In case of an error in the electrical system, the fail-safe function

stops output signals to the EPS motor. Refer to 

STC-9, "EPS SYS-

TEM : Fail-Safe"

.

• EPS control unit decreases the output signal to EPS motor while

extremely using the power steering function (e.g., full steering)

consecutively for protecting EPS motor and EPS control unit

(Overload protection control). Refer to 

STC-9, "EPS SYSTEM :

Protection Function"

.

• Extensive steering at low speed will cause the EPS control unit

and EPS motor to heat up, once temperature reaches critical point

EPS control unit will reduce current to reduce heat up. System will

recover as temperature lowers (reduced or no assistance).

EPS WARNING LAMP INDICATION

• Turn ON when there is a malfunction in EPS system. If indicates that fail-safe mode is engaged and enters a

manual steering state (Control turning force steering wheel becomes heavy).

• Also turns ON when power switch is turned ON, for purpose of lamp check. Turns OFF after the vehicle is

READY state, if system is normal.

JSGIA1000GB

JSGIA1001GB

Condition

EPS warning lamp

Power switch ON (Lamp check)

ON