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ECU Power Source Circuit: Procedure

  1. INSPECT FUSE (IGN, ECU-B, ACC) 
    1. Remove the ECU-B fuse from the engine room junction block.
    2. Remove the ACC and IGN fuses from the cowl side junction block RH.
    3. Measure the resistance of the fuses.

      Standard resistance

      Below 1 Ω

    NG → REPLACE FUSE 

    OK: Go to next step 

  2. CHECK WIRE HARNESS (MAYDAY ECU - BATTERY AND BODY GROUND) 
    1. Disconnect the U45 ECU connector.
      Fig 1: Identifying U45 ECU Connector
      GTY103328Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Measure the voltage and resistance of the wire harness side connector.

      Standard voltage

      Tester Connection Condition Specified Condition
      U45-1 (+B) - Body ground Always 10 to 14 V
      U45-13 (IG2) - Body ground Power switch ON (IG) 10 to 14 V
      U45-14 (ACC) - Body ground Power switch ON (ACC) 10 to 14 V

      Standard resistance

      Tester Connection Specified Condition
      U45-12 (E) - Body ground Below 1 Ω

    NG → REPAIR OR REPLACE HARNESS AND CONNECTOR 

    OK → REPLACE MAYDAY ECU TOGETHER WITH MAYDAY BATTERY AND THEN PERFORM REGISTRATION 

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