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HOMESERVICE MANUALSLEXUS2010LS 460L AWDREPAIR AND DIAGNOSIS (SINGLE PAGE)ACCESSORIES & EQUIPMENTANTI-THEFT SYSTEMSTHEFT DETERRENT (DIAGNOSTIC CODES & CIRCUIT TESTS)THEFT DETERRENT SYSTEMDTC B2485: SECURITY HORN CIRCUIT TRANSISTORPROCEDURE
2010 Lexus LS 460L AWD

DTC B2485: Security Horn Circuit Transistor: Procedure

2010 Lexus LS 460L AWDSECTION Procedure
  1. PERFORM ACTIVE TEST USING TECHSTREAM (SECURITY HORN) 
    1. Operate the Techstream according to the steps on the display and select "Active Test".
      BODY NO. 5

      Tester Display Test Part Control Range
      Security Horn Security horn ON / OFF

      OK

      Security horn operates normally.

    NG → See step   2 

    OK → REPLACE FRONT LIGHT ECU 

  2. INSPECT SECURITY HORN ASSEMBLY 
    1. Remove the security horn. Refer to REMOVAL .
      Fig 1: Inspecting Security Horn Assembly
      GTY174877Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Check operation of the horn.

      OK

      Measurement Condition Specified Condition
      Battery positive (+) → Terminal 1
      Battery negative (-) → Horn bracket      		 Horn sounds

    NG → See step   4 

    OK: Go to next step 

  3. CHECK HARNESS AND CONNECTOR (FRONT LIGHT ECU - SECURITY HORN) 
    1. Disconnect the A52 ECU connector.
      Fig 2: Identifying A52 ECU Connector
      GTY265011Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Disconnect the A29 horn connector.
    3. Measure the resistance according to the value(s) in the table below.

      Standard resistance

      Tester Connection Condition Specified Condition
      A52-4 (SH-) - A29-1 Always Below 1 Ω
      A52-4 (SH-) or A29-1 - Body ground Always 10 kΩ or higher

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK → REPLACE FRONT LIGHT ECU 

  4. REPLACE SECURITY HORN ASSEMBLY. Refer to  REMOVAL 
RENDER: 1.0x

NO RELATED

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When to See a Mechanic

Stop DIY work and contact a certified mechanic immediately if any of the following apply:

  • • You smell fuel, burning insulation, or see smoke.
  • • Brakes feel soft, pull hard to one side, or make grinding noises.
  • • The engine overheats, stalls repeatedly, or misfires under load.
  • • You are missing required tools, torque specs, or safe lifting equipment.
  • • You are not confident in the next step or safety outcome.