Infiniti M35/M45 Y50. Manual - part 1113

TROUBLE DIAGNOSIS

STC-9

[EPS]

C

D

E

F

H

I

J

K

L

M

A

B

STC

For Fast and Accurate Trouble Diagnosis

NGS000E1

Check the following items with the vehicle stopped

●

Is air pressure and size of tires proper?

●

Is the specified part used for the steering wheel?

●

Is control unit a genuine part?

●

Are there any fluid leakage from steering gear assembly, power steering oil pump, and hydraulic pipes,
etc? Refer to 

PS-8, "Checking Fluid Leakage"

 .

●

Is the fluid level proper? Refer to 

PS-8, "Checking Fluid Level"

 .

●

Is the wheel alignment adjusted properly? Refer to 

FSU-6, "Wheel Alignment Inspection"

  (2WD), 

FSU-24,

"Wheel Alignment Inspection"

  (AWD).

●

Are there any damage or modification to suspension or body resulting in increased weight or altered
ground clearance?

●

Check each link installation condition of suspension and axle.

●

Check each connector connection condition.

Check the following items while driving the vehicle

●

Check conditions when the malfunction occurred (5W 1H).

●

Is the engine condition normal?

Basic Inspection

NGS000E2

POWER SUPPLY CIRCUIT TERMINAL LOOSENESS AND BATTERY

Check battery terminals for looseness on both positive and negative ones and ground connection. Also make
sure that battery voltage does not drop.

Inspection: Power Steering Control Unit Power Supply Circuit and Ground

NGS000E3

1. 

CHECK POWER STEERING CONTROL UNIT CONNECTOR

Turn ignition switch OFF, disconnect power steering control unit harness connector, and check terminal for
deformation, disconnection, looseness, etc.
OK or NG

OK

>> GO TO 2.

NG

>> Connector terminal connection is loose, damaged, open, or shorted. Repair or replace the termi-

nal.

2. 

CHECK POWER STEERING CONTROL UNIT GROUND CIRCUIT

Disconnect power steering control unit harness connector M8, and
then check continuity between power steering control unit harness
connector M8 and ground.

OK or NG

OK

>> GO TO 3.

NG

>> Ground circuit open or shorted. Repair or replace any

inoperative parts.

Terminal 2 – Ground

: Continuity exist.

SGIA1231E

STC-10

[EPS]

TROUBLE DIAGNOSIS

3. 

CHECK POWER STEERING CONTROL UNIT POWER SUPPLY CIRCUIT

Turn ignition switch ON, and then check voltage between power
steering control unit harness connector M8 and ground.

OK or NG

OK

>> Power supply and ground circuit are normal.

NG

>> Power supply circuit open or shorted. Repair or replace

any inoperative parts.

Symptom: The Steering Force Does Not Change Smoothly According to the 
Vehicle Speed

NGS000E4

Heavy steering force with the static steering/light steering force during high-speed driving

1. 

POWER STEERING SOLENOID VALVE SIGNAL INSPECTION 1

1.

Start engine.

2.

Change the vehicle speed from 0 to 100 km/h (0 to 62 MPH)
slowly, and then check voltage between power steering control
unit harness connector M8 and ground.

OK or NG

OK

>> GO TO 2.

NG

>> GO TO 7.

2. 

POWER STEERING SOLENOID VALVE SIGNAL INSPECTION 2

1.

Activate fail-safe function by running the engine speed at 1,500 rpm or higher for 10 seconds with the
vehicle stopped.

2.

Change the engine speed to the idling, to approximately 1,600
rpm, and to approximately 3,000 rpm slowly, and then check
voltage between power steering control unit harness connector
M8 and ground.

OK or NG

OK

>> GO TO 3.

NG

>> GO TO 8.

3. 

CHECK POWER STEERING SOLENOID VALVE CONNECTOR

Turn ignition switch OFF, disconnect power steering solenoid valve harness connector, and check terminal for
deformation, disconnection, looseness, etc.

OK or NG

OK

>> GO TO 4.

NG

>> Harness or connector open or shorted. Repair or replace any inoperative parts.

Terminal 1 – ground

: Battery voltage (Approx. 12 V)

SGIA1232E

Terminal 7 – ground

: The voltage has changed from 
approximately 4.4 - 6.6 V to 
approximately 2.4 - 3.6 V

SGIA1233E

Terminal 7 – ground

: The voltage has changed from 
approximately 5.5 V to approxi-
mately 2.1 V step-by-step.

SGIA1233E

TROUBLE DIAGNOSIS

STC-11

[EPS]

C

D

E

F

H

I

J

K

L

M

A

B

STC

4. 

CHECK POWER STEERING SOLENOID VALVE POWER SUPPLY CIRCUIT

Check continuity between power steering control unit harness con-
nector M8 and power steering solenoid valve harness connector F25
(VQ35DE), E211 (VK45DE).

OK or NG

OK

>> GO TO 5.

NG

>> Open or short in harness. Repair or replace any inoper-

ative parts.

5. 

CHECK POWER STEERING SOLENOID VALVE GROUND CIRCUIT

Check continuity between power steering solenoid valve harness
connector F25 (VQ35DE), E211 (VK45DE) and ground.

OK or NG

OK

>> GO TO 6.

NG

>> Open or short in harness. Repair or replace any inoper-

ative parts.

6. 

CHECK POWER STEERING SOLENOID VALVE

Apply voltage power steering solenoid valve connector, and then
make sure that the operating sound (clicking sound) is heard.

OK or NG

OK

>> Perform steering wheel turning force inspection. Refer

to 

PS-10, "CHECKING STEERING WHEEL TURNING

FORCE"

 .

NG

>> Power steering solenoid valve is inoperative. Replace.

Power steering control unit

Power steering solenoid valve

Continuity

Terminal 7

Terminal 1

Yes

SGIA1235E

Terminal 2 – Ground

: Continuity exist.

SGIA1236E

Terminal 1 (+) - 2 (–)

: Operating sound is heard.

SGIA1284E

STC-12

[EPS]

TROUBLE DIAGNOSIS

7. 

CHECK VEHICLE SPEED SIGNAL CIRCUIT

Change the vehicle speed, and then check voltage waveform
between power steering control unit harness connector M8 and
ground.

OK or NG

OK

>> Power steering control unit is inoperative. Replace it.

NG

>> Check the following systems and replace if necessary.

●

Harness between unified meter & A/C amp and power steering control unit.

●

Unified meter & A/C amp and vehicle speed signal circuit Refer to 

DI-28, "UNIFIED METER

AND A/C AMP"

 .

8. 

CHECK ENGINE SPEED SIGNAL CIRCUIT

Warm up the engine, and then check voltage waveform between
power steering control unit harness connector M8 and ground when
the engine speed is the idling and at approximately 2,000 rpm.

OK or NG

OK

>> Power steering control unit is inoperating. Replace it.

NG

>> Check the following systems and replace if malfunction is detected.

●

Harness between ECM and power steering control unit

●

ECM engine speed signal circuit. Refer to 

EC-826, "CONSULT-II Function (ENGINE)"

 .

Terminal 3 – Ground

Repeat Approx. 0 V and approx. 5 V

SGIA1237E

ELF1080D

Terminal 5 – Ground

At Idle

Approx. 2,000 rpm

SGIA1289E

PBIA3654J

PBIA3655J