Nissan Versa Sedan. Instruction - part 756

STC-6

< SYSTEM DESCRIPTION >

COMPONENT PARTS

EPS Control Unit

INFOID:0000000009267346

• 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 condition.

• EPS control unit decreases the output signal to EPS motor while extremely using the power steering func-

tion (e.g., full steering) consecutively for protecting EPS motor and EPS control unit (Overload protection

control).

EPS Motor

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

Torque Sensor

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

Reduction Gear

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

umn shaft.

ABS actuator and electric unit (control unit)

• Transmits mainly the following signal to EPS control unit via 

CAN communication. 

- Vehicle speed signal (ABS)

Combination meter

• Transmits mainly the following signal to EPS control unit via 

CAN communication. 

- Vehicle speed signal (METER)
• Turns ON the EPS warning lamp according to the signal from 

EPS control unit via CAN communication.

Components parts

Reference

SYSTEM

STC-7

< SYSTEM DESCRIPTION >

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SYSTEM

EPS SYSTEM
EPS SYSTEM : System Description

INFOID:0000000009267350

• 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 condition.

• In case of an error in the electrical system, the fail-safe function stops output signals to the EPS motor. Refer

to 

STC-8, "EPS SYSTEM : Fail-Safe"

.

• EPS control unit decreases the output signal to EPS motor while extremely using the power steering func-

tion (e.g., full steering) consecutively for protecting EPS motor and EPS control unit (Overload protection

control). Refer to 

STC-8, "EPS SYSTEM : Protection Function"

.

• Extensive steering at low speed will cause the ECU and MOTOR to heat up, once temperature reaches crit-

ical point ECU will reduce current to reduce heat up. System will recover as temperature lowers (reduced or

no assistance).

SYSTEM DIAGRAM

INPUT/OUTPUT SIGNAL

Communicates the signal from each control unit via CAN communication. 

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

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

JPGIB0005GB

Control unit

Signal status

ECM

• Transmits mainly the following signals to EPS control unit via CAN communication. 
- Engine status signal 

ABS actuator and electric unit (control unit)

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

Combination meter

• Transmits mainly the following signals to EPS control unit via CAN communication. 
- Vehicle speed signal (METER)
• Receives mainly the following signals from EPS control unit via CAN communication. 
- EPS warning lamp signal 

STC-8

< SYSTEM DESCRIPTION >

SYSTEM

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

starts, if system is normal.

CAUTION:

EPS warning lamp also turns ON due to data reception error, CAN communication error etc.

EPS SYSTEM : Fail-Safe

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• If any malfunction occurs in the system and control unit detects the malfunction, EPS warning lamp in com-

bination meter turns ON to indicate system malfunction.

• When EPS warning lamp is ON, the system enters into a instruction steering state. (Steering wheel turning

force becomes heavy.)

• Under abnormal vehicle speed signal conditions, vehicle speed is judged as constant.

EPS SYSTEM : Protection Function

INFOID:0000000009267352

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).

While activating overload protection control, the assist torque gradually decreases, and the steering wheel

turning force becomes heavy. The normal assist torque reactivates by no steering.

Condition

EPS warning lamp

Ignition switch ON. (Lamp check)

ON

Engine running.

OFF

EPS system malfunction [Other diagnostic item]

ON

DIAGNOSIS SYSTEM (EPS CONTROL UNIT)

STC-9

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DIAGNOSIS SYSTEM (EPS CONTROL UNIT)

CONSULT Function

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FUNCTION

CONSULT can display each diagnostic item using the diagnostic test modes shown following.

*: The following diagnosis information is erased by erasing.

• DTC

• Freeze frame data (FFD)

ECU IDENTIFICATION

Displays the part number stored in the control unit.

SELF-DIAG RESULTS MODE

Refer to 

STC-13, "DTC Index"

.

When “CRNT” is displayed on self-diagnosis result.

• The system is presently malfunctioning.

When “PAST” is displayed on self-diagnosis result.

• System malfunction in the past is detected, but the system is presently normal.

FREEZE FRAME DATA (FFD)

The following vehicle status is recorded when DTC is detected and is displayed on CONSULT.

DATA MONITOR MODE

*1: Almost in accordance with the value of “MOTOR SIG”. It is not a malfunction though these values are not

accorded when steering quickly.

Diagnostic test mode

Function

ECU identification

The part number stored in the control unit can be read.

Self diagnostic result

Self-diagnostic results and freeze frame data can be read and erased quickly.

*

Data monitor

Input/Output data in the EPS control unit can be read.

Item name

Display item

IGN COUNTER
(0-39)

The number of times that ignition switch is turned ON after the DTC is detected is displayed.
• When “0” is displayed: It indicates that the system is presently malfunctioning.
• When except “0” is displayed: It indicates that system malfunction in the past is detected, but the system is pres-

ently normal.
NOTE:
Each time when ignition switch is turned OFF to ON, numerical number increases in 1

→2→3...38→39.

When the operation number of times exceeds 39, the number does not increase and “39” is displayed until self-
diagnosis is erased.

Monitor item (Unit)

Remarks

BATTERY VOLT (V)

Displays the power supply voltage for EPS control unit.

TORQUE SENSOR (Nm)

Displays steering wheel turning force detected by torque sensor.

MOTOR CURRENT (A)

Displays the current value consumed by EPS motor.

*1

MOTOR SIG (A)

Displays the current commanded value to EPS motor.

ASSIST TORQUE (Nm)

Displays assist torque being output by the electric power steering.

C/U TEMP (

°C or °F )

Displays the temperature of the EPS control unit.

ASSIST LEVEL (%)

Normally displays 100%. In case of an excessive stationary steering, the assist 
curvature gradually falls. However, it return to 100% when left standing.

*2

VEHICLE SPEED (km/h or MPH)

Vehicle speed is displayed from vehicle speed signal via CAN communication.

*3

WARNING LAMP (On/Off)

EPS warning lamp control status is displayed.

ENGINE STATUS (Stop/Run)

Engine speed is displayed from engine status signal via CAN communication.