Infiniti F50. Manual — part 820

ELECTRICALLY CONTROLLED POWER STEERING SYSTEM

STC-5

[EPS]

C

D

E

F

H

I

J

K

L

M

A

B

STC

TGWM0002E

STC-6

[EPS]

ELECTRICALLY CONTROLLED POWER STEERING SYSTEM

PRECAUTIONS FOR DIAGNOSIS

Intermittent problems may be caused by malfunctioning harness, harness connector or terminal. Move har-
nesses, harness connectors or terminals by hand to make sure that there is no contact malfunction.
If a circuit tester for measuring voltage is used for check, be careful not to forcibly spread any connector termi-
nals.

INSPECTION BEFORE TROUBLE DIAGNOSIS

●

Check power steering fluid level and check for any leak. Refer to

PS-6, "POWER STEERING FLUID"

.

DIAGNOSIS PROCEDURE
Symptom:

●

Heavy steering operation during stationary turns

●

Light steering operation during high-speed driving

Inspection procedure

1.

CHECK VEHICLE SPEED SIGNAL

●

Start engine and gradually increase the vehicle speed from 0 to
100 km/h (0 to 62 MPH).

●

Measure voltage between power steering control unit terminal 3
(PU/W) and body ground.

●

Check that voltage changes from approximately 5.5V to approx-
imately 2.5V. Refer to

STC-2, "SYSTEM DESCRIPTION"

.

Is the result OK?

OK

>> GO TO 5.

NG

>> GO TO 2.

2.

CHECK ENGINE SPEED SIGNAL

●

When engine is running at idle, change the engine speed to approximately 1,600 rpm and then to approx-
imately 3,000 rpm.

●

Measure voltage between power steering control unit terminal 5 (W/G) and body ground.

●

Check that voltage changes from approximately 5.5V to approximately 2.1V in steps. Refer to

STC-2,

"SYSTEM DESCRIPTION"

.

Is the result OK?

OK

>> GO TO 3.

NG

>> GO TO 9.

3.

CHECK SPEEDOMETER AND VEHICLE SPEED SENSOR

●

Check speedometer for proper operation.

●

Check that vehicle speed sensor is not regarded as malfunction in the self-diagnosis of A/T (ECM).

Is the result OK?

OK

>> GO TO 4.

NG

>>

●

Check meter and any malfunctioning parts.

CAUTION:

If rear wheels are rotated when they are off the ground,

″

the ABS wheel speed sensor is

malfunctioning

″

is display on the screen.

SGIA0046E

ELECTRICALLY CONTROLLED POWER STEERING SYSTEM

STC-7

[EPS]

C

D

E

F

H

I

J

K

L

M

A

B

STC

4.

CHECK VEHICLE SPEED SIGNAL INPUT

●

With rear wheels raised, rotate them by hand.

●

Measure voltage between terminals on power steering control unit.

Is the result OK?

OK

>> Replace power steering control unit.

NG

>> Repair or replace harness.

5.

CHECK SOLENOID VALVE

●

Disconnect the connectors for power steering control unit and
solenoid valve.

●

Check for continuity between power steering control unit termi-
nal 7 (LG) and solenoid valve terminal 1(GY).

Is the result OK?

OK

>> GO TO 6.

NG

>> Repair or replace harness.

6.

SOLENOID VALVE HARNESS INSPECTION

●

Check for continuity between the solenoid valve terminal 2 (B)
and body ground.

Is the result OK?

OK

>> GO TO 7.

NG

>> Repair or replace harness.

When the wheels are rotated slowly by hand:

3 (PU/W ) – 2 (B)

: Reading fluctuates between 0V and 5V.

3 (PU/W) – Body ground

: Reading fluctuates between 0V and 5V.

7 (LG) – 1(GY)

: Continuity should exist.

SGIA0047E

2 (B) – Body ground

: Continuity should exist.

SGIA0048E

STC-8

[EPS]

ELECTRICALLY CONTROLLED POWER STEERING SYSTEM

7.

SOLENOID VALVE INSPECTION

●

Disconnect the solenoid valve connector.

●

Check solenoid valve by listening for its operation sound while
applying battery voltage to terminals 1 (LG) and 2 (B).

●

Measure resistance value between the following solenoid valve
terminals.

Is the result OK?

OK

>> GO TO 8.

NG

>> Replace solenoid valve.

8.

STEERING WHEEL TURNING FORCE INSPECTION

Check steering wheel turning force.

Is the result OK?

OK

>> END

NG

>> Adjust steering gear assembly adjusting screw and check pump discharge pressure. Refer to

PS-

23, "CHECKING HYDRAULIC SYSTEM"

.

9.

CHECK POWER STEERING CONTROL UNIT INPUT SIGNAL

Measure the voltage between power steering control unit terminal 1
(GY) and body ground.

Is the result OK?

OK

>> GO TO 10.

NG

>> Repair or replace fuse or harness.

1 (LG) - 2 (B)

: Approx. 4 - 6

Ω

SGIA0049E

1 (GY) - Body ground

: Approx. 12V

SGIA0050E