DTC B278A: Short to GND in Immobilizer System Power Source Circuit [06/2015 - ]: Procedure

1. Using an oscilloscope, check the waveform.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a

   Component with harness connected (Power Switch)

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   -

   Measurement Condition

   Tester Connection	Condition	Tool Setting	Specified Condition
   G2-10 (VC5) - G2-6 (AGND)	Power switch off, key not in cabin, within 30 seconds after power switch pressed	2 V/DIV., 200 ms./DIV.	Pulse generation

   OK

   The waveform is similar to that shown in the illustration.

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE POWER SWITCH. Refer to  REMOVAL [06/2015 - ] 

Result: 

NG 

See step  2

1. Disconnect the G41 certification ECU (smart key ECU assembly) connector.
2. Disconnect the G2 power switch connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   G41-15 (VC5) - G2-10 (VC5)	Always	Below 1 Ω
   G41-12 (AGND) - G2-6 (AGND)	Always	Below 1 Ω
   G41-15 (VC5) or G2-10 (VC5) - Body ground	Always	10 kΩ or higher
   G41-12 (AGND) or G2-6 (AGND) - Body ground	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  3

1. Reconnect the G41 certification ECU (smart key ECU assembly) connector.
2. Reconnect the G2 power switch connector.
3. 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
   G41-15 (VC5) - G41-12 (AGND)	Power switch off, brake pedal not depressed, 30 seconds or more elapsed after driver door opened and then closed	Below 1 V

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE POWER SWITCH. Refer to  REMOVAL [06/2015 - ] 

Result: 

NG 

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY). Refer to  REMOVAL [06/2015 - 11/2018]  , or refer to  REMOVAL [11/2018 - ]