DTC B278A: Short to GND in Immobilizer System Power Source Circuit [10/2014 - ]: Procedure

1. Disconnect the D64 certification ECU (smart key ECU assembly) connector.
2. Disconnect the D46 engine switch connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   D64-1 (VC5) - D46-10 (VC5)	Always	Below 1 Ω
   D64-24 (AGND) - D46-6 (AGND)	Always	Below 1 Ω
   D64-1 (VC5) or D46-10 (VC5) - Body ground	Always	10 kΩ or higher
   D64-24 (AGND) or D46-6 (AGND) - Body ground	Always	10 kΩ or higher

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR 

Result: 

OK 

See step  2

1. Reconnect the D46 engine switch and D64 certification ECU (smart key ECU assembly) connectors.
2. Using an oscilloscope, check the waveform.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   HINT: 

   Perform this inspection on the engine switch side.

   MEASUREMENT CONDITION
   
   

   Item	Content
   Tester Connection	D46-10 (VC5) - D46-6 (AGND)
   Tool Setting	2 V/DIV., 200 ms./DIV.
   Condition	Engine switch off, key not in cabin, within 30 seconds after engine switch pressed

   OK

   The waveform is similar to that shown in the illustration.

   TEXT IN ILLUSTRATION
   
   

   *a	Component with harness connected (Engine Switch)

Result: 

OK 

REPLACE ENGINE SWITCH 

(Refer to REMOVAL [10/2014 - ] )

Result: 

NG 

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) 

(Refer to REMOVAL [10/2014 - 10/2015] Refer to REMOVAL [10/2015 - ] )