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

Toyota Venza Service Manual / Theft Deterrent / Keyless Entry / Engine Immobiliser System(w/ Smart Key System) / Short to GND in Immobiliser System Power Source Circuit (B278A)

DESCRIPTION

This DTC is stored when the engine switch power source supply line is open or shorted.

DTC No.	DTC Detection Condition	Trouble Area
B278A	Engine switch power source supply line is open or shorted.	Wire harness or connector Engine switch Certification ECU (Smart key ECU assembly)

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

If the certification ECU (smart key ECU assembly) is replaced, register the key (See page ).

PROCEDURE

1.	CHECK DTC OUTPUT

(a) Clear the DTCs (See page ).

(b) Recheck for DTCs (See page ).

OK:

DTC B278A is not output.

USE SIMULATION METHOD TO CHECK

2.	CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - ENGINE SWITCH)

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

(b) Disconnect the engine switch connector.

Standard Resistance:

Tester Connection	Condition	Specified Condition
D25-28 (VC5) - D13-14 (VC5)	Always	Below 1 Ω
D25-36 (AGND) - D13-8 (AGND)	Always	Below 1 Ω
D25-28 (VC5) - Body ground	Always	10 kΩ or higher
D25-36 (AGND) - Body ground	Always	10 kΩ or higher

Text in Illustration

Front view of wire harness connector

(to Certification ECU (Smart Key ECU Assembly))

Front view of wire harness connector

(to Engine Switch)

REPAIR OR REPLACE HARNESS OR CONNECTOR

3.	CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

(a) Reconnect the certification ECU (smart key ECU assembly) connector.

(b) Reconnect the engine switch connector.

Waveform (Reference):

Item	Content
Tester Connection	D25-28 (VC5) - D25-36 (AGND)
Tool Setting	2 V/DIV., 200 ms./DIV.
Condition	Engine switch off Key not in cabin Engine switch pressed within 30 seconds

OK:

Waveform is output normally (see illustration)

Result	Proceed to
NG	A
OK (for 2GR-FE)	B
OK (for 1AR-FE)	C

Text in Illustration

Component with harness connected

(Certification ECU (Smart Key ECU Assembly))

GND

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

REPLACE ENGINE SWITCH

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