THEFT DETERRENT / KEYLESS ENTRY: SMART KEY SYSTEM (for Start Function, HV Model): B278A; Short to GND in Immobiliser System Power Source Circuit; 2019 - 2022 MY Avalon HV [04/2018 - ]

Last Modified: 08-21-2023	6.11:8.1.0	Doc ID: RM100000001B2OD
Model Year Start: 2019	Model: Avalon HV	Prod Date Range: [04/2018 - ]
Title: THEFT DETERRENT / KEYLESS ENTRY: SMART KEY SYSTEM (for Start Function, HV Model): B278A; Short to GND in Immobiliser System Power Source Circuit; 2019 - 2022 MY Avalon HV [04/2018 - ]

DTC

B278A

Short to GND in Immobiliser System Power Source Circuit

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.

*: 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.

*a

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.

OK

REPLACE POWER SWITCH

NG

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.

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

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

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

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.

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

*a

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

OK

REPLACE POWER SWITCH

NG

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)