B278A

THEFT DETERRENT / KEYLESS ENTRY: ENGINE IMMOBILIZER SYSTEM: B278A: Short to GND in Immobilizer System Power Source Circuit
B278A - Short to GND in Immobilizer System Power Source Circuit

DESCRIPTION

When there is a short to GND in the power supply for the transponder key amplifier of the engine switch, the certification ECU stores this DTC.





* *: Only output while a malfunction is present.

Vehicle Condition and Fail-safe Operation when Malfunction Detected





Related Data List and Active Test





WIRING DIAGRAM





INSPECTION PROCEDURE

NOTICE:
* Before replacing the certification ECU, refer to Registration Engine Immobilizer System.
* The fixed 5 V power source voltage in the engine switch is output through a resistance from terminal VC5.
* Terminal AGND is grounded through both the engine switch and certification ECU.
* After performing repair, perform the operation that fulfills the DTC output confirmation operation, and then confirm that no DTCs are output again.
PROCEDURE

1. CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - ENGINE SWITCH)

(a) Disconnect the G26 ECU connector.

(b) Disconnect the G24 switch connector.

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

Standard Resistance:





NG -- REPAIR OR REPLACE HARNESS OR CONNECTOR
OK -- Continue to next step.

2. CHECK CERTIFICATION ECU

(a) Using an oscilloscope, check the waveform.





HINT
Perform this inspection on the engine switch side.

Measurement Condition





OK:

Waveform is output normally (refer to illustration).

Text in Illustration





NG -- REPLACE CERTIFICATION ECU Removal

OK -- REPLACE ENGINE SWITCH Removal