THEFT DETERRENT / KEYLESS ENTRY: ENGINE IMMOBILISER SYSTEM(w/ Smart Key System): B278A; Short to GND in Immobiliser System Power Source Circuit; 2017 - 2020 MY Sienna [08/2016

Last Modified: 04-05-2023	6.11:8.1.0	Doc ID: RM100000000ZL6M
Model Year Start: 2017	Model: Sienna	Prod Date Range: [08/2016 - ]
Title: THEFT DETERRENT / KEYLESS ENTRY: ENGINE IMMOBILISER SYSTEM(w/ Smart Key System): B278A; Short to GND in Immobiliser System Power Source Circuit; 2017 - 2020 MY Sienna [08/2016 - ]

DTC

B278A

Short to GND in Immobiliser System Power Source Circuit

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

NOTICE:

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

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

(See page )

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

(a) Disconnect the certification ECU connector.

(b) Disconnect the engine switch connector.

Standard Resistance:

REPAIR OR REPLACE HARNESS OR CONNECTOR

3.	INSPECT SMART KEY ECU ASSEMBLY

(a) Reconnect the certification ECU connector.

(b) Reconnect the engine switch connector.

Component with harness connected

(Certification ECU)

GND

Item	Content
Tester Connection	D88-28 (VC5) - D88-36 (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)

REPLACE SMART KEY ECU ASSEMBLY

(See page )