DTC B279A-12: Engine Immobiliser System Circuit Short to Battery [10/2018 - 07/2022]: Procedure

1. Turn the engine switch off.
2. Check that the connectors are properly connected to the ECM and ID code box (immobiliser code ECU).

   OK

   Connectors are properly connected.

   Result

   Proceed to
   OK
   NG

Result: 

NG 

CONNECT CONNECTORS PROPERLY 

Result: 

OK 

See step  2

1. Using an oscilloscope, check the waveform.

   Courtesy of © TOYOTA, LICENSE AGREEMENT TMS1002

   *a	Component with harness connected (ID Code Box (Immobiliser Code ECU))	*b	Waveform
   *c	Approximately 160 ms.	*d	Approximately 270 ms.

   OK

   Tester Connection	Condition	Tool Setting	Specified Condition
   F48-4 (EFIO) - Body ground	Within 3 seconds of engine start or within 3 seconds of engine switch turned on (IG) after cable disconnected and reconnected to auxiliary battery	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 ID CODE BOX (IMMOBILISER CODE ECU). Refer to  REMOVAL [10/2018 - 07/2022] 

Result: 

C 

REPLACE ECM. Refer to  REMOVAL [10/2018 - 07/2022] 

Result: 

B 

See step  3

1. Disconnect the A36 ECM connector.
2. Disconnect the F48 ID code box (immobiliser code ECU) connector.
3. Measure the resistance according to the value(s) in the table below.

   Standard Resistance

   Tester Connection	Condition	Specified Condition
   F48-4 (EFIO) - A36-26 (IMI)	Always	Below 1 Ω

   Result

   Proceed to
   OK
   NG

Result: 

OK 

REPLACE ECM. Refer to  REMOVAL [10/2018 - 07/2022] 

Result: 

NG 

REPAIR OR REPLACE HARNESS OR CONNECTOR