Toyota Avalon (XX50): System Voltage or GND Energization Malfunction (B228B). Short to GND in Immobiliser System Power Source Circuit (B278A). Malfunction of ID-BOX Recognition (B278D)

Toyota Avalon (XX50) 2019-2022 Service & Repair Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Smart Key System(for Start Function, Hv Model) / System Voltage or GND Energization Malfunction (B228B). Short to GND in Immobiliser System Power Source Circuit (B278A). Malfunction of ID-BOX Recognition (B278D)

System Voltage or GND Energization Malfunction (B228B)

DESCRIPTION

This DTC is stored when there is a malfunction in the certification ECU (smart key ECU assembly) auxiliary battery power supply circuit or ground circuit.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Note
B228B	System Voltage or GND Energization Malfunction	A malfunction is detected in the certification ECU (smart key ECU assembly) auxiliary battery power supply circuit or ground circuit. (1-trip detection logic*)	ECU-B NO. 3 fuse Wire harness or connector	Drive the vehicle.

*: 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
The hybrid control system stopped while driving.	-

Related Data List and Active Test Items

DTC No.	Data List and Active Test
B228B	-

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

When using the Techstream with the power 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, HV 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, HV Model) after confirming that the communication systems are functioning properly.
Click here
Inspect the fuses of circuits related to this system before performing the following procedure.
After repair, confirm that no DTCs are output by performing "DTC Output Confirmation Operation".

PROCEDURE

1.	CHECK HARNESS AND CONNECTOR (POWER SOURCE)

(a) Disconnect the G40 certification ECU (smart key ECU assembly) connector.

*a	Front view of wire harness connector (to Certification ECU (Smart Key ECU Assembly))

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

Standard Voltage:

Tester Connection	Condition	Specified Condition
G40-4 (+B) - Body ground	Power switch off	11 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR IN CIRCUIT CONNECTED TO POWER SOURCE

2.	CHECK HARNESS AND CONNECTOR (GROUND)

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
G40-18 (E) - Body ground	Always	Below 1 Ω

*a	Front view of wire harness connector (to Certification ECU (Smart Key ECU Assembly))

END (TEMPORARY CONNECTION FAILURE IS SUSPECTED)

REPAIR OR REPLACE HARNESS OR CONNECTOR IN CIRCUIT CONNECTED TO POWER SOURCE

Short to GND in Immobiliser System Power Source Circuit (B278A)

DESCRIPTION

When there is a short to GND in the power supply for the transponder key amplifier of the power switch, the certification ECU (smart key ECU assembly) stores this DTC.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Note
B278A	Short to GND in Immobiliser System Power Source Circuit	A short to GND in the power supply of the transponder key amplifier of the power switch (VC5 - VC5) detected. (1 trip detection logic*)	Power switch Certification ECU (smart key ECU assembly) Wire harness or connector	DTC output confirmation operation: With the shift lever in P and the electrical key transmitter sub-assembly held near the power switch, a hybrid control system start operation is performed by pressing and holding the power switch when the transmitter battery is depleted.

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Note

B278A

Short to GND in Immobiliser System Power Source Circuit

A short to GND in the power supply of the transponder key amplifier of the power switch (VC5 - VC5) detected. (1 trip detection logic*)

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

DTC output confirmation operation:

With the shift lever in P and the electrical key transmitter sub-assembly held near the power switch, a hybrid control system start operation is performed by pressing and holding the power switch when the transmitter battery is depleted.

*: 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
Hybrid control system cannot be started when transmitter battery is depleted by holding transmitter near power switch and pressing and holding power switch with shift lever in P	-

Related Data List and Active Test

DTC No.	Data List and Active Test
B278A	-

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

When using the Techstream with the power 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, HV 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, HV 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 performing repairs, confirm that no DTCs are output by performing "DTC Output Confirmation Operation".

PROCEDURE

1.	CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

(a) Using an oscilloscope, check the waveform.

Component with harness connected

(Power Switch)

HINT:

Perform this inspection on the power switch side.

Measurement Condition:

Tester Connection	Condition	Tool Setting	Specified Condition
G117-10 (VC5) - G117-6 (AGND)	Power switch off, electrical key transmitter sub-assembly not in cabin, within 30 seconds of power switch pressed	2 V/DIV., 200 ms./DIV.	Pulse generation

OK:

The waveform is similar to that shown in the illustration.

REPLACE POWER SWITCH

2.	CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - POWER SWITCH)

(a) Disconnect the G40 certification ECU (smart key ECU assembly) connector.

(b) Disconnect the G117 power switch connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
G40-7 (VC5) - G117-10 (VC5)	Always	Below 1 Ω
G40-11 (AGND) - G117-6 (AGND)	Always	Below 1 Ω
G40-7 (VC5) or G117-10 (VC5) - Other terminals and body ground	Always	10 kΩ or higher
G40-11 (AGND) or G117-6 (AGND) - Other terminals and body ground	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

3.	CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

(a) Connect the G40 certification ECU (smart key ECU assembly) connector.

(b) Connect the G117 power switch connector.

Component with harness connected

(Certification ECU (Smart Key ECU Assembly))

Standard Voltage:

Tester Connection	Condition	Specified Condition
G40-7 (VC5) - G40-11 (AGND)	Power switch off, brake pedal not depressed, 30 seconds or more after driver door opened and then closed	Below 1 V

REPLACE POWER SWITCH

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

Malfunction of ID-BOX Recognition (B278D)

DESCRIPTION

When the certification ECU (smart key ECU assembly) detects an input signal indicating that the vehicle is equipped with an ID code box even though the ID code box is not registered, the certification ECU (smart key ECU assembly) stores this DTC.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Note
B278D	Malfunction of ID-BOX Recognition	One of the following conditions is met: The certification ECU (smart key ECU assembly) recognizes that the wire harness judging whether the vehicle is equipped with an ID code box or not is provided even though the ID code box is not registered. The certification ECU (smart key ECU assembly) receives a LIN signal from the ID code box even though the ID code box is not registered. The certification ECU (smart key ECU assembly) receives a LIN signal from the ID code box even though the wire harness judging whether the vehicle is equipped with an ID code box or not is not provided.	Misconnection of the ID code box	DTC output confirmation operation: Always

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Note

B278D

Malfunction of ID-BOX Recognition

One of the following conditions is met:

The certification ECU (smart key ECU assembly) recognizes that the wire harness judging whether the vehicle is equipped with an ID code box or not is provided even though the ID code box is not registered.
The certification ECU (smart key ECU assembly) receives a LIN signal from the ID code box even though the ID code box is not registered.
The certification ECU (smart key ECU assembly) receives a LIN signal from the ID code box even though the wire harness judging whether the vehicle is equipped with an ID code box or not is not provided.

Misconnection of the ID code box

DTC output confirmation operation:

Always

Vehicle Condition and Fail-safe Operation when Malfunction Detected

Vehicle Condition when Malfunction Detected	Fail-safe Operation when Malfunction Detected
Key registration will be prohibited	-

Related Data List and Active Test

DTC No.	Data List and Active Test
B278D	-

CAUTION / NOTICE / HINT

NOTICE:

When using the Techstream with the power 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, HV 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, HV Model) after confirming that the communication systems are functioning properly.
Click here
Before performing following procedure, check that the ID code box (immobiliser code ECU) is not installed on the vehicle.
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

CLEAR DTC

(a) Clear the DTCs.

Body Electrical > Smart Key > Clear DTCs

2.	CHECK DTC OUTPUT

(a) Check for DTCs.

Body Electrical > Smart Key > Trouble Codes

HINT:

Before checking for DTCs, perform the "DTC Output Confirmation Operation" procedure.

OK:

DTC B278D is not output.

END

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

Additional Key cannot be Registered. Open in Front Floor Electrical Key Oscillator Circuit (B27A5). Open in Rear Floor Electrical Key Oscillator Circuit (B27A6)

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

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