DTC B279A: Theft Deterrent System Communication Line High Fixation [08/2019 - ]: Procedure

1. Turn the engine switch off.
2. Check that the connectors are properly connected to the ECM and certification ECU (smart key ECU assembly).

   OK

   Connectors are properly connected.

   Result

   Result	Proceed to
   The connectors are properly connected	A
   The connectors are not properly connected	B

Result: 

B 

CONNECT CONNECTORS PROPERLY 

Result: 

A 

See step  2

1. Using an oscilloscope, check the waveform.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Component with harness connected (Certification ECU (Smart Key ECU Assembly))	*b	Waveform
   *c	Approximately 160 ms.	*d	Approximately 510 ms.

   OK

   Tester Connection	Condition	Tool Setting	Specified Condition
   H197-6 (EFIO) - Body ground	Engine switch turned on (IG) using registered electrical key transmitter sub-assembly	2 V/DIV., 500 ms./DIV.	Pulse generation (See waveform)

   Result

   Result	Proceed to
   11 to 14 V	A
   Below 1 V	B
   Normal waveform	C

Result: 

A 

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY). Refer to  REMOVAL [08/2019 - ] 

Result: 

C 

REPLACE ECM. Refer to  REMOVAL [08/2015 - ] 

Result: 

B 

See step  3

1. Disconnect the A27 ECM connector.
2. Disconnect the H197 certification ECU (smart key ECU assembly) connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   H197-6 (EFIO) - A27-46 (IMI)	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE ECM. Refer to  REMOVAL [08/2015 - ] 

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR