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Home >> Infiniti >> 2008 >> G37 Base >> Repair and Diagnosis >> Steering >> Manual Steering >> Steering Control System (With 4WAS) >> Component Diagnosis >> Power Supply And Ground Circuit >> Diagnosis Procedure (4WAS Main Control Unit)
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Diagnosis Procedure (4WAS Main Control Unit)

  1. CHECK 4WAS MAIN CONTROL UNIT POWER SUPPLY
    1. Turn the ignition switch OFF.
    2. Disconnect 4WAS main control unit harness connector.
    3. Check the voltage between 4WAS main control unit harness connectors and the ground.
      VOLTAGE REFERENCE CHART

      4WAS main control unit Voltage (Approx.)
      Connector Terminal
      B54 27 - Ground 0 V
    4. Turn the ignition switch ON.
      CAUTION: Never start the engine.
    5. Check the voltage between 4WAS main control unit harness connectors and the ground.
    VOLTAGE REFERENCE CHART

    4WAS main control unit Voltage (Approx.)
    Connector Terminal
    B54 27 - Ground Battery voltage

    Is the inspection result normal? 

    YES: GO TO  2.

    NO: Check the following items. Repair or replace the malfunctioning parts.

    • 10A fuse (#45) open
    • Short among 10A fuse (#45) connector, 4WAS main control unit harness connector No. 27 terminal and the ground
    • Open between the ignition switch and 4WAS main control unit harness connector No. 27 terminal
    • Ignition switch
  2. CHECK 4WAS REAR MOTOR POWER SUPPLY CIRCUIT (1)
    1. Turn the ignition switch OFF.
    2. Remove 4WAS rear motor relay.
    3. Check the continuity between 4WAS rear motor relay harness connector and the ground.
    CONTINUITY REFERENCE CHART

    4WAS rear motor relay Continuity
    Connector Terminal
    B53 1 - Ground Existed
    2 - Ground Not existed

    Is the inspection result normal? 

    YES: GO TO  3.

    NO: Repair or replace the harnesses and connectors.

  3. CHECK 4WAS REAR MOTOR POWER SUPPLY CIRCUIT (2)

    Check the voltage between 4WAS rear motor relay harness connector and the ground.

    VOLTAGE REFERENCE CHART

    4WAS rear motor relay Voltage (Approx.)
    Connector Terminal
    B53 3 - Ground Battery voltage

    Is the inspection result normal? 

    YES: GO TO  4.

    NO: Check the following items. Repair or replace the malfunctioning parts.

    • 20A fuse (#37) open
    • Short among 20A fuse (#37) connector, 4WAS rear motor relay harness connector No. 3 terminal and the ground
    • Open between the battery and 4WAS rear motor relay harness connector No. 3 terminal
  4. CHECK 4WAS REAR MOTOR POWER SUPPLY CIRCUIT (3)
    1. Remove the noise suppressor.
    2. Check continuity between the noise suppressor harness connector and the ground.
    CONTINUITY REFERENCE CHART

    Noise suppressor Continuity
    Connector Terminal
    B51 3 - Ground Not existed
    5 - Ground
    B52 1 - Ground Not existed
    2 - Ground Existed

    Is the inspection result normal? 

    YES: GO TO  5.

    NO: Repair or replace the harnesses and connectors.

  5. CHECK 4WAS REAR MOTOR POWER SUPPLY CIRCUIT (4)
    1. Connect 4WAS main control unit harness connector.
    2. Turn the ignition switch ON.
      CAUTION: Never start the engine.
    3. Check the voltage between 4WAS main control unit harness connectors.
      VOLTAGE REFERENCE CHART

      4WAS main control unit Voltage (Approx.)
      Connector Terminal
      B54 25 - Ground Battery voltage
    4. Turn the ignition switch OFF.

    Is the inspection result normal? 

    YES: GO TO  6.

    NO: Replace 4WAS main control unit. Refer to "EXPLODED VIEW ".

  6. CHECK 4WAS REAR MOTOR RELAY
    1. Apply 12 V to 4WAS rear motor relay connector No. 1 terminal and No. 2 terminal.
      CAUTION:
      • Never make the terminals short.
      • Connect the fuse between the terminals when applying the voltage.
    2. Check the continuity between 4WAS rear motor relay connector terminals.
      CONTINUITY REFERENCE CHART

      4WAS rear motor relay Continuity
      Connector Terminal Condition
      B53 3 - 5 Apply the voltage between No. 1 terminal and No. 2 terminal. Existed
      Do not apply the voltage between No. 1 terminal and No. 2 terminal. Not existed
    3. Check the resistance between 4WAS rear motor relay connector terminals.
    RESISTANCE SPECIFICATION CHART

    4WAS rear motor relay Resistance (Approx.)
    Connector Terminal
    B53 1 - 2 50 Ω

    Is the inspection result normal? 

    YES: GO TO  7.

    NO: Replace 4WAS rear motor relay.

  7. CHECK NOISE SUPPRESSOR

    Check continuity between the noise suppressor connector terminals.

    CONTINUITY REFERENCE CHART

    Noise suppressor Continuity
    Connector Terminal Connector Terminal
    B51 3 B52 1 Existed
    B51 3 B51 5 Not existed
    B51 3 B52 2 Not existed
    B51 5 B52 2 Existed
    B51 5 B52 1 Not existed

    Is the inspection result normal? 

    YES: GO TO  8.

    NO: Replace the noise suppressor.

  8. CHECK 4WAS REAR MOTOR POWER SUPPLY
    1. Connect 4WAS main control unit harness connector.
    2. Install 4WAS rear motor relay.
    3. Install the noise suppressor.
    4. Turn the ignition switch ON.
      CAUTION: Never start the engine.
    5. Check the voltage between 4WAS main control unit harness connectors and the ground.
    VOLTAGE REFERENCE CHART

    4WAS main control unit Voltage (Approx.)
    Connector Terminal
    B54 37 - Ground Battery voltage

    Is the inspection result normal? 

    YES: INSPECTION END.

    NO: Replace 4WAS main control unit. Refer to "EXPLODED VIEW ".

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