DTC B278A: Short to GND in Immobiliser System Power Source Circuit [11/2018 - ]: Procedure

1. Using an oscilloscope, check the waveform.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a

   Component with harness connected (Power Switch)

   *b

   Waveform

   OK

   Tester Connection	Condition	Tool Setting	Specified Condition
   G55-10 (VC5) - G55-6 (AGND)	Power switch off, electrical key transmitter sub-assembly not in cabin, within 30 seconds after power switch pressed	2 V/DIV., 200 ms./DIV.	Pulse generation (See waveform)

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE POWER SWITCH. Refer to  REMOVAL [11/2018 - ] 

Result: 

NG 

See step  2

1. Disconnect the G54 certification ECU (smart key ECU assembly) connector.
2. Disconnect the G55 power switch connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   G54-7 (VC5) - G55-10 (VC5)	Always	Below 1 Ω
   G54-7 (VC5) or G55-10 (VC5) - Other terminals and body ground	Always	10 kΩ or higher
   G54-11 (AGND) - G55-6 (AGND)	Always	Below 1 Ω

4. Reconnect the G54 certification ECU (smart key ECU assembly) connector.
5. Reconnect the G55 power switch connector.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  3

1. Measure the voltage according to the value(s) in the table below.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a

   Component with harness connected (Certification ECU (Smart Key ECU Assembly))

   -

   -

   Standard Voltage

   Tester Connection	Condition	Specified Condition
   G54-7 (VC5) - G54-11 (AGND)	Power switch off, brake pedal not depressed, 30 seconds or more after driver door opened and then closed	Below 1 V

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE POWER SWITCH. Refer to  REMOVAL [11/2018 - ] 

Result: 

NG 

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY). Refer to  REMOVAL [11/2018 - 02/2019]  , or refer to  REMOVAL [02/2019 - 10/2019]  , or refer to  REMOVAL [10/2019 - 08/2020]  , or refer to  REMOVAL [08/2020 - 12/2021]  , or refer to  REMOVAL [12/2021 - 10/2022]  , or refer to  REMOVAL [10/2022 - 10/2023]  , or refer to  REMOVAL [10/2023 - ]