Toyota Yaris: Smart Key System (for Start Function) / Steering Lock System Component Internal Failure (B278196)
DESCRIPTION
The steering lock ECU and steering lock motor are built into the steering lock actuator or upper bracket assembly.
The steering lock ECU (steering lock actuator or upper bracket assembly) detects whether the steering lock is in the lock or unlock position by using the lock sensor and unlock sensor of the steering lock motor.
The steering lock ECU (steering lock actuator or upper bracket assembly) receives lock and unlock request signals from the certification ECU (smart key ECU assembly) and responds with lock and unlock operation signals.
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 |
B278196 | Steering Lock System Component Internal Failure | One 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 sensor or unlock sensor is malfunctioning (When both detection switches turn on, the system is determined to be malfunctioning).
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The steering lock motor activation circuit has a short circuit.
-
The steering lock motor activation circuit has an open circuit.
| -
Steering lock ECU (steering lock actuator or upper bracket assembly)
-
LIN communication system
| DTC Output Confirmation Operation: -
No confirmation operation is necessary (monitoring is continuous).
|

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 |
B278196 | Smart Key -
Sensor Malfunction History
-
Motor Driver Short History
-
Lock Bar Stuck Error History
|
CAUTION / NOTICE / HINT
NOTICE:
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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.
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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
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Before replacing the steering lock ECU (steering lock actuator or upper bracket assembly), refer to Registration.
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After performing repairs, confirm that no DTCs are output again.
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HINT:
When all the ECUs that are connected via LIN communication cannot communicate with the certification ECU (smart key ECU assembly), DTC B278588 is stored.
PROCEDURE
(a) Using the GTS, check if LIN communication DTC B278588 is output.
Body Electrical > Smart Key > Trouble Codes
HINT:
If a LIN communication DTC is output, perform troubleshooting for the LIN communication system.
Click here
Result | Proceed to |
DTC B278588 is output | A |
DTC B278588 is not output | B |
A |
| GO TO LIN COMMUNICATION SYSTEM (DTC B278588) |
B |
| REPLACE STEERING LOCK ECU (STEERING LOCK ACTUATOR OR UPPER BRACKET ASSEMBLY) |
DESCRIPTION If the remote engine start ECU does not respond to the certification ECU (smart key ECU assembly) or the remote engine start ID is not registered, this DTC is stored...
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...
Other information:
PRECAUTION TROUBLESHOOTING PRECAUTION NOTICE:
Since the Active Torque Split AWD System may be influenced by a malfunction in other systems, be sure to check for DTCs in the other systems.
After performing repairs, clear the DTCs and check that the DTCs are not output again...
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