Toyota Tacoma (2015-2018) Service Manual: Engine Immobiliser System Circuit Short to Battery (B279A12)

Toyota Tacoma (2015-2018) Service Manual / Engine Immobiliser / Engine Immobiliser System(w/ Smart Key System) / Engine Immobiliser System Circuit Short to Battery (B279A12)

DESCRIPTION

When the communication line (IMI - EFIO) between the ECM and certification ECU (smart key ECU assembly) is stuck high, the ECM stores this DTC.

DTC Code	DTC Detection Condition	Trouble Area	DTC Output Confirmation Operation
B279A12	The communication line (IMI - EFIO) between the ECM and certification ECU (smart key ECU assembly) is stuck high (1 trip detection logic*1).	Wire harness or connector (disconnection or break in wire harness is main cause) Certification ECU (smart key ECU assembly) ECM	Turn the engine switch on (IG) and wait 6 seconds.

*1: Only output while a malfunction is present.

Vehicle Condition and Fail-safe Operation when Malfunction Detected

Vehicle Condition when Malfunction Detected	Fail-safe Operation when Malfunction Detected
Engine cannot be started (initial ignition occurs and engine cranks, then ignition stops)	Engine cannot be started

Related Data List and Active Test

DTC Code	Data List and Active Test
B279A12	-

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

When replacing the certification ECU (smart key ECU assembly), refer to Registration (See page ).
After performing repairs, perform the operation that fulfills the DTC output confirmation operation, and then confirm that no DTCs are output again.

HINT:

When DTC B279A12 and the certification ECU (smart key ECU assembly) DTC are output simultaneously, first perform troubleshooting for the certification ECU (smart key ECU assembly) DTC.

PROCEDURE

CLEAR DTC

(a) Clear the DTCs (See page ).

2.	CHECK FOR DTC

(a) Turn the engine switch on (IG) and wait 10 seconds.

(b) Check for DTCs (See page Result ).

Result

Result	Proceed to
DTC or B279A12 is output	A
DTC or B279A12 and other DTCs are output	B

HINT:

If DTCs other than DTC B279A12 are output, troubleshoot those DTCs first.

GO TO DIAGNOSTIC TROUBLE CODE CHART

3.	CHECK CONNECTION OF CONNECTOR

(a) Turn the engine switch off.

(b) Check that the connectors are properly connected to the ECM and certification ECU (smart key ECU assembly).

OK:

Connectors are properly connected.

CONNECT CONNECTORS PROPERLY

4.	CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) - ECM)

(a) Disconnect the C27 certification ECU (smart key ECU assembly) connector.

(b) Disconnect the E14 ECM connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
C27-6 (EFIO) - E14-8 (IMI)	Always	Below 1 Ω
C27-6 (EFIO) or E14-8 (IMI) - Body ground	Always	10 kΩ or higher

REPAIR OR REPLACE HARNESS OR CONNECTOR

5.	REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

(a) Replace the certification ECU (smart key ECU assembly) with a new one (See page ).

6.	REGISTER RECOGNITION CODES

(a) Register the key (See page ).

7.	REGISTER ECU COMMUNICATION ID

(a) Register the ECU communication ID (See page ).

CLEAR DTC

(a) Clear the DTCs (See page ).

9.	CHECK FOR DTC

(a) Check for DTCs (See page HINT: ).

HINT:

Before checking for DTCs, perform the "DTC Output Confirmation Operation" procedure.

OK:

DTC B279A12 is not output.

END (CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) WAS DEFECTIVE)

REPLACE ECM

Malfunction of ID-BOX Recognition (B278D)

DESCRIPTION When the certification ECU (smart key ECU assembly) detects an input signal indicating that the vehicle is equipped with an ID code box even though the ID code box is not registered, ...

Short to GND in Immobiliser System Power Source Circuit (B278A)

DESCRIPTION When there is a short to GND in the power supply for the transponder key amplifier of the engine switch, the certification ECU (smart key ECU assembly) stores this DTC. DT ...

Other materials:

System Description
SYSTEM DESCRIPTION 1. SRS (SUPPLEMENTAL RESTRAINT SYSTEM) AIRBAG SYSTEM (a) General Description (1) The SRS airbag system consists of the following airbag and main components: Airbag Access Cab Model Double Cab Model Driver Airbag Stan ...

Inspection
INSPECTION PROCEDURE 1. INSPECT OUTER MIRROR LH (a) Check the outer mirror heater operation. Text in Illustration *a Component without harness connected (Outer Mirror LH) (1) Measure the resistance according to the value(s) ...

Starter Relay Circuit Short to Battery (P061512)
DESCRIPTION While the engine is being cranked, positive battery voltage is applied to terminal STA of the ECM. If the ECM detects the starter control (STA) signal while the vehicle is being driven, it determines that there is a malfunction in the STA circuit. The ECM then illuminates the MIL ...