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Home >> Lexus >> 2021 >> UX 250h Base >> Repair and Diagnosis (Single Page) >> Accessories & Equipment >> Anti-Theft Systems >> Smart Access System W/ Push-Button Start (Start Function) (Diagnostic Codes & Symptom Tests (1 Of 2)) (Hybrid) >> SMART ACCESS SYSTEM WITH PUSH-BUTTON START (for Start Function, HV Model) >> DTC B278A: Short to GND in Immobiliser System Power Source Circuit [10/2018 - ] >> Description

DTC B278A: Short to GND in Immobiliser System Power Source Circuit [10/2018 - ]: Description

When there is a short to GND in the power supply for the transponder key amplifier of the power 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 A short to GND in the power supply of the transponder key amplifier of the power switch (VC5 - VC5) detected. (1 trip detection logic*)
  • Power switch
  • Certification ECU (smart key ECU assembly)
  • Wire harness or connector
 DTC output confirmation operation:
  1. With the shift lever in P and the electrical key transmitter sub-assembly held near the power switch, a hybrid control system start operation is performed by pressing and holding the power switch when the transmitter battery is depleted.
  1. *: 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
Hybrid control system cannot be started when transmitter battery is depleted by holding transmitter near power switch and pressing and holding power switch with shift lever in P -
RELATED DATA LIST AND ACTIVE TEST

DTC No. Data List and Active Test
B278A -
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