DTC B278A: Short to GND in Immobilizer System Power Source Circuit [02/2014 - 11/2016]: Procedure

1. Using an oscilloscope, check the waveform.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a

   Component with harness connected (Power Switch)

   *b

   Waveform 1

   OK

   Tester Connection	Condition	Tool Setting	Specified Condition
   F49-10 (VC5) - F49-6 (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 1)

   OK

   The waveform is similar to that shown in the illustration.

   Result

   Proceed to
   OK
   NG

Result:  1

OK 

REPLACE POWER SWITCH. Refer to  REMOVAL [02/2014 - 11/2016] 

Result:  6

NG 

See step  2

1. Disconnect the F11 certification ECU (smart key ECU assembly) connector.
2. Disconnect the F49 power switch connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   F11-16 (VC5) - F49-10 (VC5)	Always	Below 1 Ω
   F11-13 (AGND) - F49-6 (AGND)	Always	Below 1 Ω
   F11-16 (VC5) or F49-10 (VC5) - Body ground	Always	10 kΩ or higher
   F11-13 (AGND) or F49-6 (AGND) - Body ground	Always	10 kΩ or higher

   Result

   Proceed to
   OK
   NG

Result:  2

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result:  1

OK 

See step  3

1. Reconnect the F11 certification ECU (smart key ECU assembly) connector.
2. Reconnect the F49 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
   F11-16 (VC5) - F11-13 (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:  1

OK 

REPLACE POWER SWITCH. Refer to  REMOVAL [02/2014 - 11/2016] 

Result:  2

NG 

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY). Refer to  REMOVAL [02/2014 - 11/2016]