Toyota Yaris: Lin Communication System / Steering Lock System Missing Message (B278187)

Toyota Yaris XP210 (2020-2026) Reapir and Service Manual / Power Source & Network / Networking / Lin Communication System / Steering Lock System Missing Message (B278187)

DESCRIPTION

This DTC is stored when LIN communication between the certification ECU (smart key ECU assembly) and steering lock ECU (steering lock actuator or upper bracket assembly) stops for 10 seconds or more.

Black Diamond car care DTC No.	Detection Item	DTC Detection Condition	Trouble Area
B278187	Steering Lock System Missing Message	No communication between certification ECU (smart key ECU assembly) and steering lock ECU (steering lock actuator or upper bracket assembly) for 10 seconds or more.	Certification ECU (smart key ECU assembly) Steering lock ECU (steering lock actuator or upper bracket assembly) Wire harness or connector

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

Inspect the fuses for circuits related to this system before performing the following procedure.
Before performing the inspection, check that DTC B2786 or B278C is not output.
Click here
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 Model Code "KEY REGIST" under manual mode and enter the following menus: Body Electrical / Entry&Start(CAN). 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.
Before replacing the certification ECU (smart key ECU assembly), ID code box (immobiliser code ECU) or steering lock ECU (steering lock actuator or upper bracket assembly), refer to Registration.

PROCEDURE

CLEAR DTC

(a) Clear the DTCs.

Body Electrical > Smart Key > Clear DTCs

2.	CHECK FOR DTC

(a) Check for DTCs.

Body Electrical > Smart Key > Trouble Codes

Result	Proceed to
DTC B278187 and B278588 are output	A
Only DTC 278187 is output	B
DTC B278187 and B278588 are not output	C

GO TO DTC CHART

USE SIMULATION METHOD TO CHECK

3.	CHECK HARNESS AND CONNECTOR (STEERING LOCK ECU (STEERING LOCK ACTUATOR OR UPPER BRACKET ASSEMBLY) - AUXILIARY BATTERY AND BODY GROUND)

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

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
H71-1 (GND) - Body ground	Always	Below 1 Ω

Standard Voltage:

Tester Connection	Switch Condition	Specified Condition
H71-7 (B) - Body ground	Ignition switch off	11 to 14 V

REPAIR OR REPLACE HARNESS OR CONNECTOR

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

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

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
H71-5 (LIN) - H46-8 (LIN)	Always	Below 1 Ω

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

REPAIR OR REPLACE HARNESS OR CONNECTOR

Door LIN Bus off (B232588)

DESCRIPTION If the main body ECU (multiplex network body ECU) detects a communication error with an ECU connected to the door bus lines for 8 seconds or more, DTC B232588 will be stored...

Communication between ECUs connected by LIN Bus off (B278588)

DESCRIPTION This DTC is stored when LIN communication between the certification ECU (smart key ECU assembly) and steering lock ECU (steering lock actuator or upper bracket assembly) stops for 10 seconds or more...

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