Toyota Venza Quiz
Theft Deterrent / Keyless Entry

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

In this manual: Theft Deterrent / Keyless Entry
Introduction — 15Maintenance — 8Audio / Video — 102Garage Door Opener — 8Navigation / Multi Info Display — 81Park Assist / Monitoring — 50Brake (front) — 7Brake (rear) — 7Brake Control / Dynamic Control Systems — 79Brake System (other) — 28Parking Brake — 22Axle And Differential — 44Drive Shaft / Propeller Shaft — 24Mf1a Transfer / 4wd / Awd — 46U660e Automatic Transmission / Transaxle — 1241ar-fe Cooling — 311ar-fe Emission Control — 101ar-fe Engine Control — 1331ar-fe Engine Mechanical — 441ar-fe Fuel — 311ar-fe Intake / Exhaust — 211ar-fe Lubrication — 111ar-fe Starting — 16Cruise Control — 241ar-fe Battery / Charging — 162gr-fe Battery / Charging — 17Networking — 67Power Distribution — 8Power Assist Systems — 34Steering Column — 37Steering Gear / Linkage — 29Alignment / Handling Diagnosis — 4Front Suspension — 39Rear Suspension — 35Tire / Wheel — 4Tire Pressure Monitoring — 35Door / Hatch — 83Exterior Panels / Trim — 56Horn — 4Lighting (ext) — 89Mirror (ext) — 36Sliding Roof / Convertible — 26Window / Glass — 87Wiper / Washer — 30Door Lock — 85Heating / Air Conditioning — 82Interior Panels / Trim — 20Lighting (int) — 37Meter / Gauge / Display — 41Mirror (int) — 9Power Outlets (int) — 10Seat — 84Seat Belt — 43Supplemental Restraint Systems — 131Theft Deterrent / Keyless Entry — 155
~2min read
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.


OK

USE SIMULATION METHOD TO CHECK
NG

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

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

(b) Disconnect the engine switch connector.

(c) Measure the resistance according to the value(s) in the table below.

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

*1

Front view of wire harness connector

(to Certification ECU (Smart Key ECU Assembly))

*2

Front view of wire harness connector

(to Engine Switch)

NG

REPAIR OR REPLACE HARNESS OR CONNECTOR
OK

  1. CHECK CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

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

(b) Reconnect the engine switch connector.

(c) Using an oscilloscope, check the waveform.


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

*1

Component with harness connected

(Certification ECU (Smart Key ECU Assembly))

*2

GND

A

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

B

REPLACE ENGINE SWITCH

C

REPLACE ENGINE SWITCH

Test yourself

A quick Toyota Venza quiz: every answer comes with an explanation and a link to the manual page.