Toyota Yaris: Smart Key System (for Start Function) / Immobiliser Amp Missing Message (B278E87)

Toyota Yaris XP210 (2020-2025) Reapir and Service Manual / Vehicle Interior / Theft Deterrent / Keyless Entry / Smart Key System (for Start Function) / Immobiliser Amp Missing Message (B278E87)

DESCRIPTION

A transponder key amplifier is built into the certification ECU (smart key ECU assembly).

When a communication malfunction occurs with the transponder key amplifier inside the certification ECU (smart key ECU assembly), this DTC is stored.

DTC No.	Detection Item	DTC Detection Condition	Trouble Area	Note
B278E87	Immobiliser Amp Missing Message	A communication malfunction with the transponder key amplifier inside the certification ECU (smart key ECU assembly) is detected. (1-trip detection logic*) do not match.	Certification ECU (smart key ECU assembly)	Any time

*: Only detected while a malfunction is present and the ignition switch is ON.

Vehicle Condition and Fail-safe Function when Malfunction Detected

Vehicle Condition when Malfunction Detected	Fail-safe Function 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.	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
B278E87	-

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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Before replacing the certification ECU (smart key ECU assembly), refer to Registration.
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After performing repairs, confirm that no DTCs are output again.

PROCEDURE

CLEAR DTC

(a) Clear the DTCs.

Body Electrical > Smart Key > Clear DTCs

2.	CHECK FOR DTC

(a) Press the engine switch with the electric key transmitter sub-assembly not in the cabin.

(b) Check for DTCs.

Body Electrical > Smart Key > Trouble Codes

Result	Proceed to
DTC B278E87 is output	A
DTC B278E87 is not output	B

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

USE SIMULATION METHOD TO CHECK

ID-BOX Component Internal Failure (B278D96)

DESCRIPTION When the certification ECU (smart key ECU assembly) detects an input signal indicating that the vehicle is equipped with an ID code box even though the ID code box is not registered, the certification ECU (smart key ECU assembly) stores this DTC...

ID-BOX Calibration / Parameter Memory Failure (B279046)

DESCRIPTION When an internal malfunction occurs in the ID code box (immobiliser code ECU), the certification ECU (smart key ECU assembly) stores this DTC...

Other information:

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Toyota Yaris XP210 (2020-2025) Reapir and Service Manual: Disassembly

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