Toyota Tacoma 2015-2018 Service Manual: Engine Immobiliser System Signal (Some Circuit Quantity, Reported via Serial Data) Invalid (B279986)

Toyota Tacoma 2015-2018 Service Manual / Engine Immobiliser / Engine Immobiliser System(w/ Smart Key System) / Engine Immobiliser System Signal (Some Circuit Quantity, Reported via Serial Data) Invalid (B279986)

DESCRIPTION

When there are communication malfunctions between the ECM and certification ECU (smart key ECU assembly), or when the communication ID codes do not match, the ECM stores this DTC.

DTC Code	DTC Detection Condition	Trouble Area	DTC Output Confirmation Operation
B279986	Either condition is met (1 trip detection logic*1): A malfunction in the communication or communication lines between the ECM and certification ECU (smart key ECU assembly) A matching communication code cannot be verified during communication between the ECM and certification ECU (smart key ECU assembly).	Certification ECU (smart key ECU assembly) ECM Wire harness or connector	Either condition is met: Within 10 seconds of an engine start operation being performed (with the shift lever in P and the brake pedal depressed, the engine switch is pressed while carrying the key). If there is a malfunction, the engine stops (communication begins within 3 seconds of the engine start operation being performed, and DTCs are stored after 6 seconds). 10 seconds after the engine switch is turned on (IG) after reconnecting the cable to the negative (-) battery terminal (communication begins within 3 seconds of the engine switch being turned on (IG), and DTCs are stored after 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	-

Related Data List and Active Test

DTC Code	Data List and Active Test
B279986	-

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 B279986 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

1.	REGISTER ECU COMMUNICATION ID

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

CLEAR DTC

(a) Clear the DTCs (See page ).

3.	CHECK FOR DTC

(a) Start the engine.

(b) Perform "DTC Output Confirmation Operation" procedure.

OK:

DTC B279986 is not output.

Result

Result	Proceed to
OK	A
NG (DTC B279986 is output)	B
NG (Other DTCs are output)	C

END (COMMUNICATION ID REGISTRATION WAS DEFECTIVE)

GO TO DIAGNOSTIC TROUBLE CODE CHART

4.	INSPECT ECM (TERMINAL IMO)

(a) Using an oscilloscope, check the waveform.

Text in Illustration

Component with harness connected

(ECM)

Waveform

Measurement Condition:

Tester Connection	Condition	Tool Setting	Specified Condition
E14-9 (IMO) - Body ground	Within 3 seconds of engine start or within 3 seconds of engine switch turned on (IG) after battery cable disconnected and reconnected	2 V/DIV., 500 ms./DIV.	Pulse generation (See waveform)

Tester Connection

Condition

Tool Setting

Specified Condition

E14-9 (IMO) - Body ground

Within 3 seconds of engine start or within 3 seconds of engine switch turned on (IG) after battery cable disconnected and reconnected

2 V/DIV., 500 ms./DIV.

Pulse generation

(See waveform)

OK:

The waveform is similar to that shown in the illustration.

Result

Result	Proceed to
Normal waveform	A
Terminal IMO stuck low (2.4 V or less)	B
Terminal IMO stuck high (12 V), or has abnormal wavelength or shape	C

GO TO STEP 8

REPLACE ECM

5.	INSPECT CERTIFICATION ECU (SMART KEY ECU ASSEMBLY) (TERMINAL IMI)

(a) Using an oscilloscope, check the waveform.

Text in Illustration

Component with harness connected

(ECM)

Waveform

Measurement Condition:

Tester Connection	Condition	Tool Setting	Specified Condition
E14-8 (IMI) - Body ground	Engine switch on (IG) using registered electrical key transmitter sub-assembly	2 V/DIV., 500 ms./DIV.	Pulse generation (See waveform)

Tester Connection

Condition

Tool Setting

Specified Condition

E14-8 (IMI) - Body ground

Engine switch on (IG) using registered electrical key transmitter sub-assembly

2 V/DIV., 500 ms./DIV.

Pulse generation

(See waveform)

OK:

The waveform is similar to that shown in the illustration.

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

6.	REGISTER ECU COMMUNICATION ID

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

7.	CHECK WHETHER ENGINE STARTS

(a) Using an electrical key transmitter sub-assembly which is registered to the vehicle, turn the engine switch on (IG).

(b) Check that the engine starts 5 seconds after the engine switch was turned on (IG).

OK:

Engine starts normally.

END (COMMUNICATION ID REGISTRATION WAS DEFECTIVE)

REPLACE ECM

8.	INSPECT ECM (IMO TERMINAL VOLTAGE)

(a) Disconnect the ECM connector.

(b) Turn the engine switch on (IG).

Standard Voltage:

Tester Connection	Condition	Specified Condition
E14-9 (IMO) - Body ground	Engine switch on (IG) using registered electrical key transmitter sub-assembly	Terminal IMO stuck low (2.4 V or less)
E14-9 (IMO) - Body ground		Terminal IMO stuck high (12 V) or abnormal waveform

Text in Illustration

*a	Front view of wire harness connector (to ECM)

Result

Result	Proceed to
Terminal IMO stuck low (2.4 V or less)	A
Terminal IMO stuck high (12 V) or abnormal waveform	B

REPLACE ECM

9.	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
C27-7 (EFII) - E14-9 (IMO)	Always	Below 1 Ω
C27-7 (EFII) or E14-9 (IMO) - Body ground	Always	10 kΩ or higher
C27-6 (EFIO) - E14-8 (IMI)	Always	Below 1 Ω
C27-6 (EFIO) or E14-8 (IMI) - Body ground	Always	10 kΩ or higher

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

REPAIR OR REPLACE HARNESS OR CONNECTOR

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