STEERING CONTROL SYSTEM
G STEERING
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SECTION STC
STEERING CONTROL SYSTEM
CONTENTS
EPS
ELECTRICALLY CONTROLLED POWER STEER-
ING SYSTEM .............................................................. 2
Precautions .............................................................. 2
BEFORE DIAGNOSING THE POW ER STE ER-
ING SYSTEM, ENSURE THAT ............................. 2
Description ............................................................... 2
SYSTEM DESCRIPTION ...................................... 2
FAIL-SAFE FUNCTION ......................................... 2
HYDRAULIC CIRCUIT .......................................... 3
Component Parts Location .......................................3
Trouble Diagnosis . ....... ...... ....... ...... ....... ...... ....... ...... 4
WIRING DIAGRAM ...............................................4
PRECAUTIONS FOR DIAGNOSIS .......................6
INSPECTION BEFORE TROUBLE DIAGNOSIS .....6
DIAGNOSIS PROCEDURE ..................................6
Control Unit Inspection Table ....................................9
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ELECTRICALLY CONTROLLED POWER STEERING SYSTEM PFP:28500 Precautions EGS0007V
BEFORE DIAGNOSING THE POWER STEERING SYSTEM, ENSURE THAT
Vehicle Stopped
1. Power steering comp onents (gea rs, oil pu mp, pip es, etc. ) Are free from leaka ge, and t hat oil le vel is c orrect.
2. T ires are inflated to specified pressure and are of specified size, and that steering wheel is a genuine Nissan part.
3. Suspension utilizes the original design, and is free of modifications which increase vehicle weight.
4. Wheel alignment is adjusted properly.
Vehicle In Operation
1. Understand the trouble symptom.
2. Engine is operation properly
Description EGS0007W
SYSTEM DESCRIPTION
The power steering system is a twin orifice type, which uses a vehicle-speed sensing, electronic control
design. Sole noid va lve sensi tiv ity is co ntrol led in res pons e to vehicl e spe ed to achi eve o ptimu m ste ering ef fo rt.
FAIL- SAFE FUNCTION
The fail-safe function operates to regulate solenoid valve operation
in response to engine speed, thereby maintaining the required steering force.
Fail-Safe Input Conditions
Fail-safe input conditions Release conditions
No vehicle speed signal entered for at least 10 seconds while
driving at an engine speed of greater than 1,500 rpm.
A vehicle speed signal of greater than 30 km/h (19 MPH) or
abruptly drops below 2 km/h (1 MPH).
NOTE:
When the engine i s revved up to 1,5 00 rpm or m ore for at least 10 second s with ve hicle at standstill , the fail safe function operates; however, this is not a matter of concer n. The fail-safe function can be released by driving vehicle of a speed of greater than 1.4 km/h (0.9 MPH) or by turning ignition switch from “OFF” to “ON”.
● A vehicle speed signal of greater than 1.4 km/h (0.9 MPH) is
entered,
● Ignition switch is turned from ″OFF″ to ″ON″.
SST696CA
SST697CB
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STC-2
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HYDRAULIC CIRCUIT
[EPS]
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STC
SST838C
NOTE:
On models equ ipp ed wi t h acti ve d ampe r susp en si on s ys tem, t he so le no id v al ve i s cont r oll ed b y ac tive d am pe r
suspension co nt rol u nit , a s s ho wn in t he ab ov e d r awi ng . Fo r ″ Wiring Diagrams ″ and ″ Trouble Diagnoses ″ of
these models. Refer to SCS-2, "
Component Parts Location EGS0007X
TROUBLE DIAGNOSIS FOR ACTIVE DAMPER SUSPENSION" .
SGIA0042E
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Trouble Diagnosis EGS0007Y
WIRING DIAGRAM
TGWM0001E
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PRECAUTIONS FOR DIAGNOSIS
Intermittent problems may be caused by malfunctioning harness, harness connector or terminal. Move harnesses, 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 terminals.
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 increa se the vehic le spee d fro m 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, "
OK or NG
OK >> GO TO 5.
NG >>GO TO 2.
SYSTEM DESCRIPTION" .
SGIA0046E
2. CHECK ENGINE SPEED SIGNAL
● When engine is running at idl e, 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" .
OK or NG
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).
OK or NG
OK >> GO TO 4.
NG >>
● Check meter and a ny malfunctioning parts.
CAUTION:
If rear wheels are ro tated when they a r e off the gro und, “the ABS w hee l sp ee d s en sor is
malfunctioning” is display on the screen.
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4. CHECK VEHICLE SPEED SIGNAL INPUT
● With rear wheels raised, rotate them by hand.
● Measure voltage between terminals on power steering control unit.
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.
OK or NG
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 valv e.
● Check for continuity between power steering control unit termi-
nal 7 (LG) and solenoid valve terminal 1 (GY).
7 (LG) – 1 (GY) : Continuity should exist.
OK or NG
OK >> GO TO 6.
NG >> Repair or replace harness.
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6. SOLENOID VALVE HARNESS INSPECTION
● Check for continuity between the solenoid valve terminal 2 (B)
and body ground.
2 (B) – Body ground : Continuity should exist.
OK or NG
OK >> GO TO 7.
NG >> Repair or replace harness.
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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 resis tance value b etween the following solenoid valve
terminals.
1 (LG) - 2 (B) : Approx. 4 - 6Ω
OK or NG
OK >> GO TO 8.
NG >>Replace solenoid valve.
[EPS]
8. STEERING WHEEL TURNING FORCE INSPECTION
Check steering wheel turning force.
OK or NG
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.
1 (GY) - Body ground : Approx. 12V
OK or NG
OK >> GO TO 10.
NG >> Repair or replace fuse or harness.
SGIA0049E
SGIA0050E
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10. POWER STEERING CONTROL UNIT GROUND INSPECTION
Check for continuity between the power steering control unit terminal
2 (B) and body gr ound.
2 (B) - Body ground : Continuity should exist
OK or NG
OK >> GO TO 11.
NG >> Repair or replace harness.
11. ENGINE REVOLUTION SIGNAL INSPECTION
Check power steering control unit terminal 5 (W/G),. Refer to STC-9,
"Control Unit Inspection Table" .
OK or NG
OK >> GO TO 1.
NG >> Check harness between ECM and control unit or ECM.
Repair or replace harness if necessary.
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Control Unit Inspection Table EGS0007Z
The standard values (voltage), measured with an analog tester in contact with control unit terminal, are shown
below:
Inspection terminal
(Power steering control unit)
1
2 Ground 0V
3 Vehicle speed signal
5
7 Solenoid valve
Condition Application Standard
Power Battery voltage (approx. 12V)
Ignition switch ON
Engine revolution signal
Engine running
When the speed is very low, the voltage fluctuates between approximately 0V and approx imately 5V or higher.
Measure the tachometer drive signal.
Refer to EC-109, "
Terminal Layout"
Normal
0 km/h ((0 MPH) : Approx. 4.4 - 6.6V
100 km/h (62 MPH): Approx. 2.4 - 3.6V
When the fail-safe function is activated:
0 - 1,500 rpm : Approx. 4.4 - 6.6V
1,500 - 3,000 rpm : Approx. 3.5V
3,000 rpm or more: Approx. 2.1V
ECM Harness Connector
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Revision: 2004 April 2002 Q45
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