SYS.OK|MANUAL.DB● LIVE
HOMESERVICE MANUALSSCION2015FR-S AUTOMATIC TRANSREPAIR AND DIAGNOSIS (SINGLE PAGE)ACCESSORIES & EQUIPMENTANTI-THEFT SYSTEMSENGINE IMMOBILISER SYSTEM (DIAGNOSTIC CODES & SYMPTOM TESTS)ENGINE IMMOBILIZER SYSTEMDTC B1409: SCU COMMUNICATION CIRCUIT [05/2014 - ]PROCEDURE
2015 Scion FR-S Automatic Trans

DTC B1409: SCU Communication Circuit [05/2014 - ]: Procedure

2015 Scion FR-S Automatic TransSECTION Procedure
  1. CHECK HARNESS AND CONNECTOR (INSTRUMENT PANEL JUNCTION BLOCK - BATTERY, BODY GROUND) 
    1. Disconnect the A73 and D6 main body ECU (network gateway ECU) connectors.
    2. Disconnect the 3A, 3B and 3C instrument panel junction block assembly connectors.
    3. Measure the voltage according to the value(s) in the chart below.
      GTY387686Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      TEXT IN ILLUSTRATION

      *a Front view of wire harness connector
      (to Instrument Panel Junction Block Assembly)

      Standard Voltage

      Tester Connection Condition Specified Condition
      3A-27 - Body ground Always 11 to 14 V
      3C-19 - Body ground Always 11 to 14 V
    4. Measure the resistance according to the value(s) in the chart below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      3B-18 - Body ground Always Below 1 Ω
      A73-4 (GND) - Body ground Always Below 1 Ω
      D6-1 (GND) - Body ground Always Below 1 Ω

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to next step 

  2. INSPECT INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY 
    1. Remove the instrument panel junction block assembly. Refer to REMOVAL [05/2014 - ] .
    2. Remove the main body ECU (network gateway ECU) from the instrument panel junction block assembly.
    3. Measure the resistance according to the value(s) in the chart below.
      GTY391652Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002
      TEXT IN ILLUSTRATION

      *a Component without harness connected
      (Instrument Panel Junction Block Assembly)      		 - -

      Standard Resistance

      Tester Connection Condition Specified Condition
      MB-1 (BECU) - 3A-27 Always Below 1 Ω
      MB-32 (BMPX) - 3C-19 Always Below 1 Ω
      MB-11 (GND) - 3B-18 Always Below 1 Ω

    NG → See step   7 

    OK: Go to next step 

  3. CHECK HARNESS AND CONNECTOR (TRANSPONDER KEY ECU ASSEMBLY - BATTERY, BODY GROUND) 
    1. Disconnect the A64 transponder key ECU assembly connector.
    2. Measure the voltage according to the value(s) in the chart below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A64-1 (+B) - Body ground Always 11 to 14 V
    3. Measure the resistance according to the value(s) in the chart below.

      Standard Resistance

      Tester Connection Condition Specified Condition
      A64-5 (GND) - Body ground Always Below 1 Ω

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to next step 

  4. CHECK HARNESS AND CONNECTOR (MAIN BODY ECU - TRANSPONDER KEY ECU ASSEMBLY) 
    1. Measure the voltage and resistance according to the value(s) in the charts below.

      Standard Voltage

      Tester Connection Condition Specified Condition
      A73-17 (UART) - Body ground Always Below 1 V

      Standard Resistance

      Tester Connection Condition Specified Condition
      A73-17 (UART) - A64-3 (UART) Always Below 1 Ω
      A73-17 (UART) - Body ground Always 10 kΩ or higher

    NG → REPAIR OR REPLACE HARNESS OR CONNECTOR 

    OK: Go to next step 

  5. REPLACE TRANSPONDER KEY ECU ASSEMBLY 
    1. Replace the transponder key ECU assembly with a new one. Refer to REMOVAL [05/2014 - ] .

      HINT: 

      • Do not register the transponder key ECU assembly.
      • Once the transponder key ECU assembly is registered to a vehicle, it cannot be used in other vehicle.

    NEXT: Go to next step 

  6. CHECK FOR DTC 
    1. Check for DTCs. Refer to DTC CHECK / CLEAR [05/2014 - ] .

      OK

      DTC B1409 is not output

      HINT: 

      • If DTC P1409 is output, reinstall the transponder key ECU assembly and then replace the main body ECU (network gateway ECU).
      • If DTC P1409 is not output, register the transponder key ECU assembly.

    NG → See step   8 

    OK → END (TRANSPONDER KEY ECU ASSEMBLY WAS DEFECTIVE) 

  7. REPLACE INSTRUMENT PANEL JUNCTION BLOCK ASSEMBLY. Refer to  REMOVAL [05/2014 - ] 
  8. REPAIR MAIN BODY ECU (NETWORK GATEWAY ECU). Refer to  REMOVAL [05/2014 - ] 
RENDER: 1.0x

NO RELATED

Recommended Tools & Savings

Use the Manual With the Right Hardware

Pair factory procedures with proven DIY tools so the instructions are easier to execute.

Affiliate disclosure: We may earn a commission at no extra cost to you.

Shop Manual-Ready ToolsFree Quote CheckQuote Shield Pro

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.