THEFT DETERRENT / KEYLESS ENTRY: SMART KEY SYSTEM (for Start Function, Gasoline Model): B278A; Short to GND in Immobiliser System Power Source Circuit; 2019 - 2024 MY RAV4 [11/2018 - ]

Last Modified: 01-30-2024	6.11:8.1.0	Doc ID: RM100000001G225
Model Year Start: 2019	Model: RAV4	Prod Date Range: [11/2018 - ]
Title: THEFT DETERRENT / KEYLESS ENTRY: SMART KEY SYSTEM (for Start Function, Gasoline Model): B278A; Short to GND in Immobiliser System Power Source Circuit; 2019 - 2024 MY RAV4 [11/2018 - ]

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 engine 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	Short to GND detected in the power supply of the transponder key amplifier of the engine switch (VC5 - VC5) (1 trip detection logic*).	Harness or connector Engine switch Certification ECU (smart key ECU assembly)	DTC Output Confirmation Operation: With the shift state park (P) and the electrical key transmitter sub-assembly held near the engine switch, an engine start operation is performed by pressing and holding the engine 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
Engine cannot be started when transmitter battery is depleted by holding electrical key transmitter sub-assembly near engine switch and pressing and holding engine switch with shift state park (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 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) 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 certification ECU (smart key ECU assembly), refer to the 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) Using an oscilloscope, check the waveform.

*a

Component with harness connected

(Engine Switch)

*b

Waveform

OK:

Tester Connection

Condition

Tool Setting

Specified Condition

G55-10 (VC5) - G55-6 (AGND)

Engine switch off, electrical key transmitter sub-assembly not in cabin, within 30 seconds after engine switch pressed

2 V/DIV., 200 ms./DIV.

Pulse generation

(See waveform)

OK

REPLACE ENGINE SWITCH

NG

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

(a) Disconnect the G54 certification ECU (smart key ECU assembly) connector.

(b) Disconnect the G55 engine switch connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
G54-7 (VC5) - G55-10 (VC5)	Always	Below 1 Ω
G54-7 (VC5) or G55-10 (VC5) - Other terminals and body ground	Always	10 kΩ or higher
G54-11 (AGND) - G55-6 (AGND)	Always	Below 1 Ω

(d) Reconnect the G54 certification ECU (smart key ECU assembly) connector.

(e) Reconnect the G55 engine switch connector.

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR

OK

3.	CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

(a) 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
G54-7 (VC5) - G54-11 (AGND)	Engine switch off, brake pedal not depressed, 30 seconds or more after driver door opened and then closed	Below 1 V

OK

REPLACE ENGINE SWITCH

NG

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)