ENGINE IMMOBILISER SYSTEM, Diagnostic DTC:B278A

DTC Code DTC Name
B278A Short to GND in Immobiliser System Power Source Circuit

DESCRIPTION

This DTC is output when the engine switch power source supply line is open or shorted.

DTC No. DTC Detection Condition Trouble Area
B278A Engine switch power source supply line is open or shorted

  • Wire harness or connector

  • Engine switch

  • Certification ECU (Smart key ECU assembly)

WIRING DIAGRAM

A016363E06

INSPECTION PROCEDURE

Note

If the certification ECU (smart key ECU assembly) is replaced, register the key.

PROCEDURE


  1. CHECK DTC OUTPUT


    1. Clear the DTCs Click here.

    2. Recheck for DTCs.

      OK
      B278A output does not recur.

    NG

    CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - ENGINE SWITCH) Click here

    OK

    USE SIMULATION METHOD TO CHECK Click here

  2. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - ENGINE SWITCH)


    1. Disconnect the certification ECU (smart key ECU assembly) connector.

    2. A015YXJE08

      Disconnect the engine switch connector.

    3. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      P33-30 (VC5) - J31-14 (VC5) Always Below 1 Ω
      P33-40 (AGND) - J31-8 (AGND) Always Below 1 Ω
      P33-17 (E) - Body ground Always Below 1 Ω
      P33-30 (VC5) - Body ground Always 10 kΩ or higher
      P33-40 (AGND) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  3. CHECK HARNESS AND CONNECTOR (ENGINE SWITCH POWER SOURCE AND BODY GROUND)


    1. Reconnect the certification ECU (smart key ECU assembly) connector.

    2. A01626GE08

      Reconnect the engine switch connector.

    3. Measure the voltage according to the value(s) in the table below.

      Standard Voltage
      Tester Connection Condition Specified Condition
      P33-30 (VC5) - Body ground Key is not in cabin Below 1 V
      P33-30 (VC5) - Body ground Brake pedal is depressed 4.6 to 5.4 V

    4. Measure the resistance according to the value(s) in the table below.

      Standard Resistance
      Tester Connection Condition Specified Condition
      P33-40 (AGND) - Body ground Always Below 1 Ω

    NG

    REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

    OK

    REPLACE ENGINE SWITCH Click here