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Power Steering Control System: Overview Nissan 370Z I

Steering Control Systems 7 illustrations ~1142 words

System Description

  1. The EPS system controls the power steering solenoid valve through the power steering control unit.
  2. The valve driving voltage to control the power steering solenoid valve varies according to the vehicle speed.

Scheme 1

Scheme 1
Scheme 1

OPERATION PRINCIPLE

During Parking (When Turning The Steering Wheel To The Right.)

Scheme 2

Scheme 2: OPERATION PRINCIPLE
Scheme 2: OPERATION PRINCIPLE
  1. Power steering solenoid valve is closed while a vehicle is stopped.
  2. Pinion "1R", "2R" and "3R" are closed depending on steering torque of steering wheel.
  3. Oil pressure "P" in the gear housing assembly is the sum of oil pressures occurred in "2R" and "3R". This results in a light steering force because of high pressure.

During High-speed Operation (When Turning The Steering Wheel To The Right.)

Scheme 3

Scheme 3
Scheme 3
  1. Power steering solenoid valve is opened during high-speed operation.
  2. Pinion "1R", "2R" and "3R" are closed depending on steering torque of steering wheel.
  3. Oil pressure "2R" does not occur because the power steering solenoid valve is on full throttle.
  4. Oil pressure "P" in the gear housing assembly includes only oil pressure occurred in "3R" and results in a heavy steering force.

Scheme 4

Scheme 4: Component Parts Location
Scheme 4: Component Parts Location

Component Description

Component partsReference/Function
Power steering control unitSignals from various sensors control the driving voltage to the power steering solenoid valve. The power steering control unit controls the driving voltage to the power steering solenoid valve for maintaining the power steering assist force when the fail-safe function is activated. (The engine speed signals control EPS system if any vehicle speed signal error is detected.)
Combination meter" DESCRIPTION "
ECM" DESCRIPTION "
Power steering solenoid valve" DESCRIPTION "

COMPONENT DESCRIPTION

Description

Power steering solenoid valve controls the power steering oil pressure in the gear housing assembly.

ECM sends engine speed signal to power steering control unit.

Scheme 5

Scheme 5: Diagnosis Procedure
Scheme 5: Diagnosis Procedure
  1. PERFORM ECM SELF-DIAGNOSIS With CONSULT-III Turn the ignition switch ON. CAUTION: Never start the engine Perform "ENGINE" self-diagnosis. Refer to " «CONSULT-III FUNCTION»(/nissan/370z/i-2008-2014/remont/engine-control-systems/#engine-control-system) ". Is any DTC detected? YES: Check the DTC. NO: GO TO 2.
  2. CHECK HARNESS BETWEEN ECM AND POWER STEERING CONTROL UNIT Turn the ignition switch OFF. Disconnect ECM harness connectors. Disconnect power steering control unit harness connector. Check the continuity between ECM harness connector and power steering control unit harness connector. CONTINUITY SPECIFICATION ECM Power steering control unit Continuity Connector Terminal Connector Terminal M107 110 M108 10 Existed Check the continuity between power steering control unit harness connector and ground. CONTINUITY SPECIFICATION Power steering control unit - Continuity Connector Terminal M108 10 Ground Not existed Is the inspection result normal? YES: GO TO 3. NO: Repair or replace error-detected parts.
  3. CHECK ENGINE SPEED SIGNAL (1) Connect ECM harness connectors. Turn the ignition switch ON. Check the signal between ECM harness connector and ground with oscilloscope. VOLTAGE SPECIFICATION ECM - Condition Voltage (Approx.) Connector Terminal M107 110 Ground Engine is running Warm-up condition Idle speed Engine is running Warm-up condition Engine speed: Approx. 2,000 RPM Is the inspection result normal? YES: GO TO 4. NO: Replace ECM. Refer to " «ADDITIONAL SERVICE WHEN REPLACING CONTROL UNIT (ECM) : DESCRIPTION»(/nissan/370z/i-2008-2014/remont/engine-control-systems/#engine-control-system) ".
  4. CHECK ENGINE SPEED SIGNAL (2) Turn the ignition switch OFF. Connect power steering control unit harness connector. Check the signal between power steering control unit harness connector and ground with oscilloscope. VOLTAGE SPECIFICATION ECM - Condition Voltage (Approx.) Connector Terminal M108 10 Ground Engine is running Warm-up condition Idle speed Engine is running Warm-up condition Engine speed: Approx. 2,000 RPM Is the inspection result normal? YES: GO TO 5. NO: Replace power steering control unit. Refer to " «REMOVAL AND INSTALLATION»(ref-402689-S12233880812011053100000) ".
  5. CHECK TERMINALS AND HARNESS CONNECTORS Check the power steering control unit pin terminals for damage or loose connection with harness connector. Check the ECM pin terminals for damage or loose connection with harness connector. Is the inspection result normal? YES: INSPECTION END NO: Repair or replace error-detected parts.

Combination meter sends vehicle speed signal to power steering control unit.

Scheme 6

Scheme 6: Diagnosis Procedure
Scheme 6: Diagnosis Procedure
  1. PERFORM COMBINATION METER SELF-DIAGNOSIS With CONSULT-III Turn the ignition switch ON. CAUTION: Never start the engine Perform "METER/M&A" self-diagnosis. Refer to " «CONSULT-III FUNCTION (METER/M&A)»(ref-402677-S34068714502011053100000) ". Is any DTC detected? YES: Check the DTC. NO: GO TO 2.
  2. CHECK HARNESS BETWEEN COMBINATION METER AND POWER STEERING CONTROL UNIT Turn the ignition switch OFF. Disconnect combination meter harness connector. Disconnect power steering control unit harness connector. Check the continuity between combination meter harness connector and power steering control unit harness connector. CONTINUITY SPECIFICATION Combination meter Power steering control unit Continuity Connector Terminal Connector Terminal M53 3 M108 8 Existed Check the continuity between power steering control unit harness connector and ground. CONTINUITY SPECIFICATION Power steering control unit - Continuity Connector Terminal M108 8 Ground Not existed Is the inspection result normal? YES: GO TO 3. NO: Repair or replace error-detected parts.
  3. CHECK VEHICLE SPEED SIGNAL (1) Connect combination meter harness connector. Check the combination meter input/output standard values. Refer to " «REFERENCE VALUE»(ref-402677-S12432866782011053100000) ". Is the inspection result normal? YES: GO TO 4. NO: Replace combination meter Refer to " «EXPLODED VIEW»(ref-402677-S16585634822011053100000) ".
  4. CHECK VEHICLE SPEED SIGNAL (2) Turn the ignition switch OFF. Connect power steering control unit harness connector. Check the signal between power steering control unit harness connector and ground with oscilloscope. VOLTAGE SPECIFICATION Power steering control unit - Condition Voltage (Approx.) Connector Terminal M108 8 Ground Vehicle speed: 40 km/h (25 MPH) CAUTION: Check air pressure of tire under standard condition. NOTE: The maximum voltage varies depending on the specification (destination unit). Is the inspection result normal? YES: GO TO 5. NO: Replace power steering control unit. Refer to " «REMOVAL AND INSTALLATION»(ref-402689-S12233880812011053100000) ".
  5. CHECK TERMINALS AND HARNESS CONNECTORS
  1. Check the power steering control unit pin terminals for damage or loose connection with harness connector.
  2. Check the combination meter pin terminals for damage or loose connection with harness connector.

Is the inspection result normal?

YES: INSPECTION END

NO: Repair or replace error-detected parts.

Scheme 7

Scheme 7: TERMINAL LAYOUT
Scheme 7: TERMINAL LAYOUT
  1. Hard steering when fully turning the steering wheel.
  2. Light steering when driving at a high speed.

OPERATION PROCEDURE

  1. Connect both battery cables. NOTE: Supply power using jumper cables if battery is discharged.
  2. Turn the ignition switch to ACC position. (At this time, the steering lock will be released.)
  3. Disconnect both battery cables. The steering lock will remain released with both battery cables disconnected and the steering wheel can be turned.
  4. Perform the necessary repair operation.
  5. When the repair work is completed, re-connect both battery cables. With the brake pedal released, turn the ignition switch from ACC position to ON position, then to LOCK position. (The steering wheel will lock when the ignition switch is turned to LOCK position.)
  6. Perform self-diagnosis check of all control units using CONSULT.
  1. Connect both battery cables. NOTE: Supply power using jumper cables if battery is discharged.
  2. Turn the ignition switch to ACC position. (At this time, the steering lock will be released.)
  3. Disconnect both battery cables. The steering lock will remain released with both battery cables disconnected and the steering wheel can be turned.
  4. Perform the necessary repair operation.
  5. When the repair work is completed, re-connect both battery cables. With the brake pedal released, turn the ignition switch from ACC position to ON position, then to LOCK position. (The steering wheel will lock when the ignition switch is turned to LOCK position.)
  6. Perform self-diagnosis check of all control units using CONSULT.

See also:
• CONSULT-III FUNCTION

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