Toyota Yaris: Smart Key System (for Start Function) / Power Source Control System Circuit Short to Ground (B278211)

Toyota Yaris XP210 (2020-2024) Reapir and Service Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Smart Key System (for Start Function) / Power Source Control System Circuit Short to Ground (B278211)

DESCRIPTION

The certification ECU (smart key ECU assembly) has a power source mode switching function.

This DTC is stored when the IGE input (the steering lock motor activation permission signal) sent directly from the certification ECU (smart key ECU assembly) to the steering lock ECU (steering lock actuator or upper bracket assembly) is determined to be abnormal.

HINT:

The steering lock ECU (steering lock actuator or upper bracket assembly) is not connected to the CAN communication system. However, the steering lock ECU (steering lock actuator or upper bracket assembly) is connected to the certification ECU (smart key ECU assembly) via LIN communication and communicates with other components via CAN communication through the certification ECU (smart key ECU assembly).

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Note
B278211	Power Source Control System Circuit Short to Ground	Either of the following conditions is met (1-trip detection logic (Only output while a malfunction is present and the ignition switch is ON.)): The steering lock motor activation command circuit has a short circuit. The steering lock motor activation command circuit has an open circuit. HINT: If the power supply signal from the LIN communication line does not match the power supply signal from the direct line, the system is determined to be malfunctioning.	Steering lock ECU (steering lock actuator or upper bracket assembly) Certification ECU (smart key ECU assembly) Wire harness or connector	Perform a steering lock/unlock operation. (The steering locks when a door is opened and the ignition switch off. The steering unlocks when the ignition switch is turned to ACC or ON while carrying the key.)

DTC No.

Detection Item

DTC Detection Condition

Trouble Area

Note

B278211

Power Source Control System Circuit Short to Ground

Either of the following conditions is met (1-trip detection logic (Only output while a malfunction is present and the ignition switch is ON.)):

The steering lock motor activation command circuit has a short circuit.
The steering lock motor activation command circuit has an open circuit.

HINT:

If the power supply signal from the LIN communication line does not match the power supply signal from the direct line, the system is determined to be malfunctioning.

Steering lock ECU (steering lock actuator or upper bracket assembly)
Certification ECU (smart key ECU assembly)
Wire harness or connector

Perform a steering lock/unlock operation. (The steering locks when a door is opened and the ignition switch off. The steering unlocks when the ignition switch is turned to ACC or ON while carrying the key.)

Vehicle Condition and Fail-safe Function when Malfunction Detected

Vehicle Condition when Malfunction Detected	Fail-safe Function when Malfunction Detected
The steering cannot be locked or unlocked. For this reason, the engine cannot be started.	Prohibits the engine from being started (the engine does not start).

Related Data List and Active Test Items

DTC No.	Data List and Active Test
B278211	-

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 the vehicle type under manual mode and enter the following menus: Body Electrical / Smart Key. 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.
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When disconnecting the cable from the negative (-) auxiliary battery terminal, some systems need to be initialized after the cable is reconnected.
Before replacing the steering lock ECU (steering lock actuator or upper bracket assembly) or certification ECU (smart key ECU assembly), refer to Registration.
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PROCEDURE

1.	CHECK FOR DTC

(a) Perform the DTC output confirmation operation.

(b) Check if DTC B278588 is output.

Body Electrical > Smart Key > Trouble Codes

Result	Proceed to
DTC B278588 is not output	A
DTC B278588 is output	B

GO TO LIN COMMUNICATION SYSTEM (DTC B278588)

2.	CHECK STEERING LOCK ECU (STEERING LOCK ACTUATOR OR UPPER BRACKET ASSEMBLY)

(a) Check the signal waveform according to the condition(s) in the table below.

Measurement Condition

Item	Content
Tester Connection	H71-3 (IGE) - H71-1 (GND)
Tool Setting	2 V/DIV., 200 ms./DIV.
Condition	Steering lock motor operating when all conditions met, and then door opened: Steering unlocked Ignition switch turned off

Component with harness connected

(Steering Lock ECU (Steering Lock Actuator or Upper Bracket Assembly))

Steering lock motor not operating

Steering lock motor operating

GO TO STEP 5

3.	CLEAR DTC AND DATA LIST MALFUNCTION RECORD

(a) Clear the DTCs.

Body Electrical > Smart Key > Clear DTCs

(b) Disconnect the cable from the negative (-) auxiliary battery terminal, wait for 30 seconds or more, and then reconnect the cable to the negative (-) auxiliary battery terminal to clear the record of malfunctions stored in the Data List.

CAUTION:

After turning the ignition switch off, waiting time may be required before disconnecting the cable from the auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the auxiliary battery terminal notices before proceeding with work.

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4.	CHECK FOR DTC

(a) Perform the DTC output confirmation operation.

(b) Check if DTC B278215 is output.

Body Electrical > Smart Key > Trouble Codes

Result	Proceed to
DTC B278215 is not output	A
DTC B278215 is output	B

SYSTEM RETURNED TO NORMAL (DTC STORED DUE TO BAD CONNECTION, BUT SYSTEM RETURNED TO NORMAL BY RECONNECTING CONNECTOR)

REPLACE STEERING LOCK ECU (STEERING LOCK ACTUATOR OR UPPER BRACKET ASSEMBLY)

5.	CHECK HARNESS AND CONNECTOR (STEERING LOCK ECU (STEERING LOCK ACTUATOR OR UPPER BRACKET ASSEMBLY) - CERTIFICATION ECU (SMART KEY ECU ASSEMBLY))

(a) Disconnect the H71 steering lock ECU (steering lock actuator or upper bracket assembly) connector.

(b) Disconnect the H46 certification ECU (smart key ECU assembly) connector.

OK:

There is no deformation or corrosion of the connector case or terminals.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
H71-3 (IGE) - H46-24 (SLR+)	Always	Below 1 Ω
H71-1 (GND) - Body ground	Always	Below 1 Ω
H71-3 (IGE) or H46-24 (SLR+) - Other terminals and body ground	Always	10 kΩ or higher

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

REPAIR OR REPLACE HARNESS OR CONNECTOR

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DESCRIPTION The certification ECU (smart key ECU assembly) has a power source mode switching function. This DTC is stored when the IGE input (the steering lock motor activation permission signal) sent directly from the certification ECU (smart key ECU assembly) to the steering lock ECU (steering lock actuator or upper bracket assembly) is determined to be abnormal...

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