DTC B278A: Short to GND in Immobiliser System Power Source Circuit [08/2019 - ]: Description

WARNING: This page is about a different car, the 2022 Toyota Sequoia, 2021 Toyota Sequoia, and 2020 Toyota Sequoia. However, it is still accessible from the selected car via links, so may be relevant.

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	-