Nissan Versa

 Sedan Service Manual

Steering » Steering control system (STC)
EPS System

EPS SYSTEM : System 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 condition.
• In case of an error in the electrical system, the fail-safe function stops output signals to the EPS motor. Refer to STC "EPS SYSTEM : 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 "EPS SYSTEM : Protection Function".
• Extensive steering at low speed will cause the ECU and MOTOR to heat up, once temperature reaches critical 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 manual steering state (Control turning force steering wheel becomes heavy).
• 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

• If any malfunction occurs in the system and control unit detects the malfunction, EPS warning lamp in combination meter turns ON to indicate system malfunction.
• When EPS warning lamp is ON, the system enters into a manual steering state. (Steering wheel turning force becomes heavy.)
• Under abnormal vehicle speed signal conditions, vehicle speed is judged as constant.

EPS SYSTEM : Protection Function

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.

Precautions

EPS System

Diagnosis system (EPS control unit)

EPS control unit

Diagnosis and repair workflow

C1601 Battery power supply

C1604 Torque sensor

C1606 EPS Motor

C1607, C1608 EPS Control unit

C1609 Vehicle speed signal

C1610 Engine status signal

U1000 CAN Comm circuit

EPS Warning lamp

EPS Warning lamp does not turn OFF

Steering wheel turning force is heavy or light

Unbalance steering wheel turning force and return between right and left

Unbalance steering wheel turning force (torque variation)

EPS Control unit