Toyota Corolla Cross Owners & Service Manuals

Toyota Corolla Cross: Engine Immobiliser System Circuit Short to Battery (B279A12)

Toyota Corolla Cross (2022-2024) Service Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Smart Key System (for Start Function, Gasoline Model) / Engine Immobiliser System Circuit Short to Battery (B279A12)

DESCRIPTION

If the communication line (IMI - EFIO) between the ECM and ID code box (immobiliser code ECU) is stuck high, the ECM will store this DTC.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Note

B279A12

Engine Immobiliser System Circuit Short to Battery

The communication line (IMI - EFIO) between the ECM and ID code box (immobiliser code ECU) is stuck high. (1 trip detection logic*)
  • ID code box (immobiliser code ECU)
  • ECM
  • Wire harness or connector

DTC output confirmation operation:

  • Turn the ignition switch to ON and wait 6 seconds.
  • *: Only output while a malfunction is present.
Vehicle Condition and Fail-safe Operation when Malfunction Detected

Vehicle Condition when Malfunction Detected

Fail-safe Operation when Malfunction Detected

Engine cannot be started

Engine cannot be started
Related Data List and Active Test

DTC No.

Data List and Active Test

B279A12

-

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

  • When using the GTS with the ignition switch off, connect the GTS to the DLC3 and turn a courtesy light switch on and off at intervals of 1.5 seconds or less until communication between the GTS and the vehicle begins. Then select the vehicle type under manual mode and enter the following menus: Body Electrical / Smart Key. While using the GTS, periodically turn a courtesy light switch on and off at intervals of 1.5 seconds or less to maintain communication between the GTS and the vehicle.
  • The smart key system (for Start Function) uses the LIN communication system and CAN communication system. Inspect the communication function by following How to Proceed with Troubleshooting. Troubleshoot the smart key system (for Start Function) after confirming that the communication systems are functioning properly.

    Click here

  • Before replacing the ECM or ID code box (immobiliser code ECU), refer to Registration.

    Click here

  • After performing repairs, confirm that no DTCs are output by performing "DTC Output Confirmation Operation".
  • When the ECM is replaced, update the ECU security key.

    Click here

HINT:

When DTC B279A12 and the certification ECU (smart key ECU assembly) DTC are output simultaneously, first perform troubleshooting for the certification ECU (smart key ECU assembly) DTC.

PROCEDURE

1.

CHECK CONNECTION OF CONNECTOR

(a) Turn the ignition switch off.

(b) Check that the connectors are properly connected to the ECM and ID code box (immobiliser code ECU).

OK:

Connectors are properly connected.

NG

CONNECT CONNECTORS PROPERLY
OK

2.

CHECK WHETHER ENGINE STARTS

(a) Check that the engine starts.

OK:

Engine starts normally.

OK

USE SIMULATION METHOD TO CHECK

NG

3.

CHECK ECM (TERMINAL EFIO)

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

Standard Voltage:

Tester Connection

Switch Condition

Specified Condition

I20-4 (EFIO) - Body ground

Ignition switch ON

11 to 14 V

*a

Component with harness connected

(ID Code Box (Immobiliser Code ECU))
NG

GO TO STEP 5

OK

4.

CHECK ID CODE BOX (IMMOBILISER CODE ECU) (TERMINAL EFIO)

(a) Using an oscilloscope, check the waveform.

*a

Component with harness connected

(ID Code Box (Immobiliser Code ECU))

*b

Waveform

*c

Approximately 160 ms.

*d

Approximately 270 ms.

OK:

Tester Connection

Condition

Tool Setting

Specified Condition

I20-4 (EFIO) - Body ground

Within 3 seconds of engine start or within 3 seconds of ignition switch turned ON after cable disconnected and reconnected to auxiliary battery

2 V/DIV., 500 ms./DIV.

Pulse generation

(See waveform)
OK

REPLACE ECM

NG

REPLACE ID CODE BOX (ID CODE BOX)

5.

CHECK HARNESS AND CONNECTOR (ID CODE BOX (IMMOBILISER CODE ECU) - ECM)

(a) Disconnect the A47 ECM connector.

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

Standard Resistance:

Tester Connection

Condition

Specified Condition

I20-4 (EFIO) - A47-26 (IMI)

Always

Below 1 Ω
OK

REPLACE ECM

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

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