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Home >> Lexus >> 2009 >> RX 350 FWD >> Repair and Diagnosis >> Suspension >> Rear Suspension >> Air Suspension System (Diagnostic Codes & Circuit Tests) >> Air Suspension System >> DTC C1774/74: Power Source Circuit >> Procedure

DTC C1774/74: Power Source Circuit: Procedure

  1. CHECK SOURCE VOLTAGE 
    1. Check the positive battery voltage.

      Standard voltage

      10 to 14 V

    NG → REPLACE BATTERY 

    OK: Go to next step 

  2. INSPECT FUSE (AIR SUS) 
    1. Remove the AIR SUS fuse from the instrument panel J/B.
      Fig 1: Locating AIR SUS Fuse
      GTY136728Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Check fuse.
      1. Check continuity of the AIR SUS fuse.

        Standard

        Continuity

    NG → REPLACE FUSE 

    OK: Go to next step 

  3. INSPECT FUSE (ECU-IG NO. 1) 
    1. Remove the ECU-IG NO. 1 fuse from the instrument panel J/B.
    2. Check fuse.
      1. Check continuity of the ECU-IG NO. 1fuse.

        Standard

        Continuity

        Result

        Result Proceed to
        OK A
        (When using Techstream)
        (Reference)
        B
        (When not using Techstream)
        NG C

    C → REPLACE FUSE 

    B → See step   5 

    A: Go to next step 

  4. INSPECT SUSPENSION CONTROL ECU 
    1. Connect the Techstream to the DLC3.
    2. Turn the ignition switch to the ON position, and push the Techstream main switch on.
    3. Select the item below in the DATA LIST, and read its value displayed on the Techstream.

      Air suspension

      Item Normal Condition
      IG Power Source Voltage Actual ECU power supply voltage: 10 to 14 V
      +B Power Source Voltage Actual ECU power supply voltage: 10 to 14 V
    4. Check the voltage.

      Voltage

      10 to 14 V

    NG → See step   6 

    OK → REPLACE SUSPENSION CONTROL ECU 

  5. INSPECT SUSPENSION CONTROL ECU 
    1. Remove the suspension control ECU with connectors being connected.
      Fig 2: Identifying Suspension Control ECU Connector Terminals
      GTY155220Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Turn the ignition switch to the ON position.
    3. Measure the voltage according to the values in the table below.

      Standard voltage

      Tester Connection Specified Condition
      S15-6 (B) - S16-1 (GND) 10 to 14 V
      S15-6 (B) - S15-5 (GND2) 10 to 14 V
      S16-10 (IG) - S16-1 (GND) 10 to 14 V
      S16-10 (IG) - S15-5 (GND2) 10 to 14 V

    NG → Go to next step 

    OK → REPLACE SUSPENSION CONTROL ECU 

  6. CHECK HARNESS AND CONNECTOR (SUSPENSION CONTROL ECU - BODY GROUND) 
    1. Disconnect the suspension control ECU S15 and S16 connectors.
      Fig 3: Identifying Suspension Control ECU S15 & S16 Connectors
      GTY154791Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Measure the resistance according to the values in the table below.

      Standard resistance

      Tester Connection Specified Condition
      S16-1 (GND) - Body ground Below 1 Ω
      S15-5 (GND2) - Body ground Below 1 Ω

      Result

      Result Proceed to
      NG Repair or replace the harness or the connector between the suspension control ECU and body ground.
      OK When B terminal malfunctions:
      Repair or replace the harness or the connector between the AIR SUS fuse and the suspension control ECU.
      When IG terminal malfunctions:
      Repair or replace the harness or the connector between the ECU-IG NO. 1 fuse and the suspension control ECU.

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK → REPLACE SUSPENSION CONTROL ECU 

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