Toyota Avalon (XX50): Engine Immobiliser System Circuit Short to Battery (B279A12). Engine Immobiliser System Incorrect Assembly (B279C95). Ignition Hold Monitor Malfunction (B2271)

Toyota Avalon (XX50) 2019-2022 Service & Repair Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Smart Key System(for Start Function, Gasoline Model) / Engine Immobiliser System Circuit Short to Battery (B279A12). Engine Immobiliser System Incorrect Assembly (B279C95). Ignition Hold Monitor Malfunction (B2271)

Engine Immobiliser System Circuit Short to Battery (B279A12)

DESCRIPTION

If the communication line (IMI - EFIO) between the ECM and certification ECU (smart key ECU assembly) 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 certification ECU (smart key ECU assembly) is stuck high. (1 trip detection logic*)	Certification ECU (smart key ECU assembly) ECM Wire harness or connector	DTC output confirmation operation: Turn the engine switch on (IG) and wait 6 seconds.

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 certification ECU (smart key ECU assembly) is stuck high. (1 trip detection logic*)

Certification ECU (smart key ECU assembly)
ECM
Wire harness or connector

DTC output confirmation operation:

Turn the engine switch on (IG) 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 Techstream with the engine switch off, connect the Techstream to the DLC3 and turn a courtesy light switch on and off at intervals of 1.5 seconds or less until communication between the Techstream and the vehicle begins. Then select the vehicle type under manual mode and enter the following menus: Body Electrical / Smart Key. While using the Techstream, periodically turn a courtesy light switch on and off at intervals of 1.5 seconds or less to maintain communication between the Techstream and the vehicle.
The smart key system (for Start Function, Gasoline Model) 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, Gasoline Model) after confirming that the communication systems are functioning properly.
Click here
Before replacing the ECM or certification ECU (smart key ECU assembly), refer to Registration.
Click here
After performing repairs, confirm that no DTCs are output by performing "DTC Output Confirmation Operation".

HINT:

When DTC B279A12 and a 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 engine switch off.

(b) Check that the connectors are properly connected to the ECM and certification ECU (smart key ECU assembly).

OK:

Connectors are properly connected.

CONNECT CONNECTORS PROPERLY

2.	CHECK WHETHER ENGINE STARTS

(a) Check that the engine starts.

OK:

Engine starts normally.

USE SIMULATION METHOD TO CHECK

CHECK ECM

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
A10-4 (EFIO) - Body ground	Engine switch on (IG)	11 to 14 V

*a	Component with harness connected (Certification ECU (Smart Key ECU Assembly))

GO TO STEP 5

4.	CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) (TERMINAL EFIO)

(a) Connect the A10 certification ECU (smart key ECU assembly) connector.

(b) Using an oscilloscope, check the waveform.

Component with harness connected

(Certification ECU (Smart Key ECU Assembly))

Waveform

Approximately 160 ms.

Approximately 270 ms.

OK:

Tester Connection	Condition	Tool Setting	Specified Condition
A10-4 (EFIO) - Body ground	Engine switch turned on (IG) using registered electrical key transmitter sub-assembly	2 V/DIV., 500 ms./DIV.	Pulse generation (See waveform)

Tester Connection

Condition

Tool Setting

Specified Condition

A10-4 (EFIO) - Body ground

Engine switch turned on (IG) using registered electrical key transmitter sub-assembly

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

Pulse generation

(See waveform)

REPLACE ECM

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

5.	CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - ECM)

(a) Disconnect the A18 ECM connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
A10-4 (EFIO) - A18-59 (IMI)	Always	Below 1 Ω

REPLACE ECM

REPAIR OR REPLACE HARNESS OR CONNECTOR

Engine Immobiliser System Incorrect Assembly (B279C95)

DESCRIPTION

If an ECM that is incompatible with the immobiliser function is installed, the ECM will store this DTC.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Note
B279C95	Engine Immobiliser System Incorrect Assembly	An ECM that is incompatible with the immobiliser function is installed. (1-trip detection logic*)	ECM	-

*: Only detected while a malfunction is present.

Vehicle Condition and Fail-safe Function when Malfunction Detected

Vehicle Condition when Malfunction Detected	Fail-safe Function when Malfunction Detected
Engine cannot be started	-

Related Data List and Active Test

DTC No.	Data List and Active Test
B279C95	-

CAUTION / NOTICE / HINT

NOTICE:

When using the Techstream with the engine switch off, connect the Techstream to the DLC3 and turn a courtesy light switch on and off at intervals of 1.5 seconds or less until communication between the Techstream and the vehicle begins. Then select the vehicle type under manual mode and enter the following menus: Body Electrical / Smart Key. While using the Techstream, periodically turn a courtesy light switch on and off at intervals of 1.5 seconds or less to maintain communication between the Techstream and the vehicle.
The smart key system (for Start Function, Gasoline Model) 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, Gasoline Model) after confirming that the communication systems are functioning properly.
Click here
Before replacing the ECM, refer to Registration.
Click here
After performing repairs, confirm that no DTCs are output by performing "DTC Output Confirmation Operation".

PROCEDURE

1.	REPLACE ECM

(a) Temporarily replace the ECM with a new one.

Click here

END (ECM WAS DEFECTIVE)

Ignition Hold Monitor Malfunction (B2271)

DESCRIPTION

This DTC is stored when a malfunction in the IG circuit or IG hold circuit of the certification ECU (smart key ECU assembly) is detected.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Note
B2271	Ignition Hold Monitor Malfunction	When either of the following conditions is met (1-trip detection logic1): The IG circuit of the certification ECU (smart key ECU assembly) is malfunctioning.2 The IG hold circuit of the certification ECU (smart key ECU assembly) is malfunctioning.*3	Certification ECU (smart key ECU assembly) Wire harness or connector	Turn the engine switch on (IG).

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Note

B2271

Ignition Hold Monitor Malfunction

When either of the following conditions is met (1-trip detection logic*1):

The IG circuit of the certification ECU (smart key ECU assembly) is malfunctioning.*2
The IG hold circuit of the certification ECU (smart key ECU assembly) is malfunctioning.*3

Certification ECU (smart key ECU assembly)
Wire harness or connector

Turn the engine switch on (IG).

*1: Only detected while a malfunction is present and the engine switch is on (IG).
*2: The IG circuit and IG hold circuit activate the IG relay.
*3: After the IG circuit turns on, even if the certification ECU (smart key ECU assembly) malfunctions, the IG hold circuit will maintain the power source mode in on (IG).

Vehicle Condition and Fail-safe Function when Malfunction Detected

Vehicle Condition when Malfunction Detected	Fail-safe Function when Malfunction Detected
The engine switch cannot be turned on (IG) (the engine cannot be started).	The power source mode cannot be changed to on (IG).

Related Data List and Active Test Items

DTC No.	Data List and Active Test
B2271	Power Source Control IG Relay Monitor (Inside) Latch Circuit Starting Control Ignition

DTC No.

Data List and Active Test

B2271

Power Source Control

IG Relay Monitor (Inside)
Latch Circuit

Starting Control

Ignition

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

When using the Techstream with the engine switch off, connect the Techstream to the DLC3 and turn a courtesy light switch on and off at intervals of 1.5 seconds or less until communication between the Techstream and the vehicle begins. Then select the vehicle type under manual mode and enter the following menus: Body Electrical / Smart Key. While using the Techstream, periodically turn a courtesy light switch on and off at intervals of 1.5 seconds or less to maintain communication between the Techstream and the vehicle.
The smart key system (for Start Function, Gasoline Model) 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, Gasoline Model) after confirming that the communication systems are functioning properly.
Click here
Before replacing the certification ECU (smart key ECU assembly), refer to Registration.
Click here
After repair, confirm that no DTCs are output by performing "DTC Output Confirmation Operation".

PROCEDURE

1.	CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
G40-17 (IG1D) - Body ground	Engine switch on (ACC) → Engine switch on (IG)	1 V or less → 9 V or higher

*a	Component with harness connected (Certification ECU (Smart Key ECU Assembly))

END (TEMPORARY CONNECTION FAILURE IS SUSPECTED)

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

System Voltage or GND Energization Malfunction (B228B). Short to GND in Immobiliser System Power Source Circuit (B278A). Malfunction of ID-BOX Recognition (B278D)

ACC Monitor Malfunction (B2274). Detecting Vehicle Submersion (B2277). Engine/Power Switch Malfunction (B2278)

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