ENGINE IMMOBILISER SYSTEM, Diagnostic DTC:B2796, B2798

DTC Code DTC Name
B2796 No Communication in Immobiliser System
B2798 Communication Malfunction No. 2

DESCRIPTION

DTC B2796 is stored when a key is inserted into the ignition key cylinder but no communication occurs between the key and transponder key ECU assembly.

DTC B2798 is stored when a key is inserted into the ignition key cylinder but a communication error occurs between the key and transponder key ECU assembly.

DTC Code DTC Detection Condition Trouble Area DTC Output Confirmation Operation
B2796 The key code cannot be transmitted (1 trip detection logic*).

  • Key

  • Transponder key amplifier

  • Harness or connector

  • Transponder key ECU assembly

 Insert the key into the ignition key cylinder
B2798 Key code identification cannot be completed within the specified time (1 trip detection logic*). Key Insert the key into the ignition key cylinder

Vehicle Condition and Fail-safe Operation when Malfunction Detected
Vehicle Condition when Malfunction Detected Fail-safe Operation when Malfunction Detected
Engine cannot be started. -
Related Data List and Active Test
DTC Code Data List and Active Test
B2796 Response
B2798 Frame Error

WIRING DIAGRAM

A01E1CHE02

INSPECTION PROCEDURE

Note


  • When replacing the transponder key ECU assembly, refer to the Service Bulletin.

  • After performing repairs, perform the operation that fulfills the DTC output confirmation operation, and then confirm that no DTCs are output again.

PROCEDURE


  1. CLEAR DTC


    1. Clear the DTCs Click here.


    NEXT

  2. CHECK FOR DTC


    1. Check for DTCs Click here.

      OK
      DTC B2796 or B2798 is not output.

    NG

    READ VALUE USING INTELLIGENT TESTER (ENGINE IMMOBILISER SYSTEM) Click here

    OK

    USE SIMULATION METHOD TO CHECK Click here

  3. READ VALUE USING INTELLIGENT TESTER (ENGINE IMMOBILISER SYSTEM)


    1. Use the Data List to check if the engine immobiliser system is functioning properly Click here.

      Immobiliser
      Item Measurement Item/Range Normal Condition Diagnostic Note
      Immobiliser Engine immobiliser system status determined by transponder key ECU assembly / Set or Unset

      Set: Engine immobiliser set (engine start prohibited [no key in ignition key cylinder])

      Unset: Engine immobiliser unset (engine start permitted [key inserted in ignition key cylinder])

      		 When the engine immobiliser system does not change to the unset state, this item can be used to determine if the cause is the transponder key ECU assembly.
      OK
      Set (the key is not inserted in the ignition key cylinder) and Unset (the key is inserted in the ignition key cylinder) appear on the screen according to the key insertion condition.

    NG

    CHECK WHETHER ENGINE STARTS WITH OTHER KEY Click here

    OK

    REPLACE TRANSPONDER KEY ECU ASSEMBLY

  4. CHECK WHETHER ENGINE STARTS WITH OTHER KEY


    1. Check whether the engine starts with an already registered vehicle key.

      OK
      Engine starts.

    NG

    CHECK HARNESS AND CONNECTOR (TRANSPONDER KEY ECU - TRANSPONDER KEY AMPLIFIER) Click here

    OK

    REREGISTER OR REPLACE KEY THAT CANNOT START ENGINE

  5. CHECK HARNESS AND CONNECTOR (TRANSPONDER KEY ECU - TRANSPONDER KEY AMPLIFIER)


    1. Disconnect the T21 transponder key ECU assembly connector.

    2. Disconnect the T20 transponder key amplifier connector.

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

      Standard Resistance
      Tester Connection Condition Specified Condition
      T21-14 (VC5) - T20-1 (VC5) Always Below 1 Ω
      T21-15 (CODE) - T20-4 (CODE) Always Below 1 Ω
      T21-4 (TXCT) - T20-5 (TXCT) Always Below 1 Ω
      T21-5 (AGND) - T20-7 (AGND) Always Below 1 Ω
      T21-14 (VC5) or T20-1 (VC5) - Body ground Always 10 kΩ or higher
      T21-15 (CODE) or T20-4 (CODE) - Body ground Always 10 kΩ or higher
      T21-4 (TXCT) or T20-5 (TXCT) - Body ground Always 10 kΩ or higher
      T21-5 (AGND) or T20-7 (AGND) - Body ground Always 10 kΩ or higher

    NG

    REPAIR OR REPLACE HARNESS OR CONNECTOR

    OK

  6. REPLACE TRANSPONDER KEY AMPLIFIER


    1. Temporally replace the transponder key amplifier with a new or normally functioning one Click here.


    NEXT

  7. CHECK WHETHER ENGINE STARTS


    1. Check that the engine starts normally.

      OK
      Engine starts.

    NG

    REPLACE TRANSPONDER KEY ECU ASSEMBLY

    OK

    END (TRANSPONDER KEY AMPLIFIER IS DEFECTIVE)