Last Modified: 07-31-2024 6.11:8.1.0 Doc ID: RM100000002BENK
Model Year Start: 2023 Model: GR Corolla Prod Date Range: [03/2023 -           ]
Title: THEFT DETERRENT / KEYLESS ENTRY: SMART KEY SYSTEM (for Start Function, Gasoline Model): B279A12; Engine Immobiliser System Circuit Short to Battery; 2023 - 2025 MY Corolla Corolla Hatchback GR Corolla [03/2023 -        ]

DTC

B279A12

Engine Immobiliser System Circuit Short to Battery

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 Model Code "KEY REGIST" under manual mode and enter the following menus: Body Electrical / Start Key(CAN). 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 2023 - 2025 MY Corolla Corolla Hatchback GR Corolla [11/2022 -        ]; THEFT DETERRENT / KEYLESS ENTRY: SMART KEY SYSTEM (for Start Function, Gasoline Model): HOW TO PROCEED WITH TROUBLESHOOTING

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

    Click here 2023 - 2025 MY Corolla Corolla Hatchback GR Corolla [11/2022 -        ]; THEFT DETERRENT / KEYLESS ENTRY: SMART KEY SYSTEM (for Start Function, Gasoline Model): REGISTRATION

  • After performing repairs, confirm that no DTCs are output by performing "DTC Output Confirmation Operation".

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

Pre-procedure1

(a) Turn the ignition switch off.

Procedure1

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

OK:

Connectors are properly connected.

Post-procedure1

(c) None

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

Condition

Specified Condition

I20-4 (EFIO) - Body ground

Engine switch on (IG)

11 to 14 V

Result:

Proceed to

OK

NG

*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 to ON after cable disconnected and reconnected to auxiliary battery

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

Pulse generation

(See waveform)
OK

REPLACE ECM

for M20A-FKS: Click here 2023 - 2025 MY Corolla Corolla Hatchback [03/2023 -        ]; M20A-FKS (ENGINE CONTROL): ECM: REMOVAL

for G16E-GTS: Click here 2023 - 2025 MY GR Corolla [11/2022 -        ]; G16E-GTS (ENGINE CONTROL): ECM: REMOVAL

NG

REPLACE ID CODE BOX (IMMOBILISER CODE ECU)

5.

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

Pre-procedure1

(a) Disconnect the A47*1, A178*2 or A139*3 ECM connector.

  • *1: for M20A-FKS (except K121 CVT)
  • *2: for M20A-FKS (K121 CVT)
  • *3: for G16E-GTS

(b) Disconnect the I20 ID code box (immobiliser code ECU) connector.

Procedure1

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

Standard Resistance:

for M20A-FKS (except K121 CVT):

Tester Connection

Condition

Specified Condition

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

Always

Below 1 Ω

for M20A-FKS (K121 CVT):

Tester Connection

Condition

Specified Condition

I20-4 (EFIO) - A178-54 (IMI)

Always

Below 1 Ω

for G16E-GTS:

Tester Connection

Condition

Specified Condition

I20-4 (EFIO) - A139-61 (IMI)

Always

Below 1 Ω

Post-procedure1

(d) None

OK

REPLACE ECM

for M20A-FKS: Click here 2023 - 2025 MY Corolla Corolla Hatchback [03/2023 -        ]; M20A-FKS (ENGINE CONTROL): ECM: REMOVAL

for G16E-GTS: Click here 2023 - 2025 MY GR Corolla [11/2022 -        ]; G16E-GTS (ENGINE CONTROL): ECM: REMOVAL

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR