2012 Lexus IS 250C Automatic TransFACTORY OEM SERVICE PROCEDURE

DTC P0724: Brake Switch "B" Circuit High: Procedure

  1. READ VALUE USING TECHSTREAM (STOP LIGHT SWITCH) 
    1. Connect the Techstream to the DLC3.
    2. Turn the engine switch on (IG).
    3. Turn the Techstream on.
    4. Enter the following menus: Powertrain / Engine / Data List / All Data / Stop Light Switch.
    5. Read the value displayed on the Techstream.

      OK

      Item Measurement Item/Range Normal Condition
      Stop Light Switch Stop light switch assembly status/
      ON or OFF
      • ON: Brake pedal depressed
      • OFF: Brake pedal released

    NG → See step   2 

    OK → See step   6 

  2. INSPECT STOP LIGHT SWITCH ASSEMBLY 
    1. Inspect the stop light switch assembly. Refer to INSPECTION .

    NG → See step   5 

    OK: Go to next step 

  3. CHECK HARNESS AND CONNECTOR (ECM - STOP LIGHT SWITCH ASSEMBLY) 
    1. Disconnect the ECM connector.
      Fig 1: ECM Connector
      GTY349919Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
    2. Measure the voltage according to the value(s) in the table below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A6-4 (STP) - Body ground Brake pedal depressed 7.5 to 14 V
      A6-4 (STP) - Body ground Brake pedal released Below 1.5 V
      TEXT IN ILLUSTRATION

      *a Front view of wire harness connector
      (to ECM)
    3. Reconnect the ECM connector.

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR (ECM - STOP LIGHT SWITCH ASSEMBLY) 

    OK → See step   4 

  4. REPLACE ECM. Refer to  REMOVAL 
  5. REPLACE STOP LIGHT SWITCH ASSEMBLY. Refer to  REMOVAL 
  6. CHECK FOR INTERMITTENT PROBLEMS. Refer to  CHECK FOR INTERMITTENT PROBLEMS 
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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.

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