Toyota Venza: Lost Communication with Power Source Control (B278C)

Toyota Venza Service Manual / Networking / Lin Communication System / Lost Communication with Power Source Control (B278C)

DESCRIPTION

This DTC is stored when LIN communication between the certification ECU (smart key ECU assembly) and power management control ECU stops for more than 10 seconds.

DTC Code	DTC Detection Condition	Trouble Area
B278C	No communication between the certification ECU (smart key ECU assembly) and power management control ECU for more than 10 seconds.	Power management control ECU Certification ECU (Smart key ECU assembly) Wire harness or connector AM2 fuse

WIRING DIAGRAM

CAUTION / NOTICE / HINT

NOTICE:

If the certification ECU (smart key ECU assembly) is replaced, register the key.
When using the Techstream to troubleshoot with the ignition switch off:
Connect the Techstream to the DLC3, and turn the courtesy switch on and off at 1.5-second intervals until communication between the Techstream and vehicle begins.

PROCEDURE

1.	CHECK HARNESS AND CONNECTOR (POWER MANAGEMENT CONTROL ECU - BATTERY AND BODY GROUND)

(a) Disconnect the D43 ECU connector.

(b) Measure the resistance and voltage according to the value(s) in the table below.

Standard Resistance:

Tester Connection	Condition	Specified Condition
D43-5 (GND2) - Body ground	Always	Below 1 Ω
D43-6 (GND) - Body ground	Always	Below 1 Ω

Standard Voltage:

Tester Connection	Condition	Specified Condition
D43-1 (AM22) - Body ground	Always	11 to 14 V
D43-2 (AM21) - Body ground	Always	11 to 14 V

Text in Illustration

*1	Power Management Control ECU

REPAIR OR REPLACE HARNESS OR CONNECTOR

2.	CHECK HARNESS AND CONNECTOR (CERTIFICATION ECU - POWER MANAGEMENT CONTROL ECU)

(a) Disconnect the D25 ECU connector.

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

Standard Resistance:

Tester Connection	Condition	Specified Condition
D25-29 (LIN) - D43-24 (LIN2)	Always	Below 1 Ω
D25-29 (LIN) - 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 Power Management Control ECU)

REPAIR OR REPLACE HARNESS OR CONNECTOR

3.	REPLACE POWER MANAGEMENT CONTROL ECU

(a) Replace the power management control ECU (See page ).

4.	CHECK DTC OUTPUT

(a) Clear the DTC (See page ).

(b) Recheck for DTCs.

OK:

DTC B278C is not output.

END (POWER MANAGEMENT CONTROL ECU WAS DEFECTIVE)

REPLACE CERTIFICATION ECU (SMART KEY ECU ASSEMBLY)

Data List / Active Test

DATA LIST / ACTIVE TEST 1. DATA LIST HINT: Using the Techstream to read the Data List allows the values or states of switches, sensors, actuators and other items to be read without removing any p ...

Diagnostic Trouble Code Chart

DIAGNOSTIC TROUBLE CODE CHART Main Body ECU (Driver Side junction Block Assembly) DTC Code Detection Item Trouble Area See page B1206 ...

Other materials about Toyota Venza:

System Diagram
SYSTEM DIAGRAM Communication Table Sender Receiver Signal Line Main body ECU (Driver side junction block assembly) Sliding roof ECU (Sliding roof drive gear sub-assembly) Key ...

Receiver Error (C2176/76)
DESCRIPTION The signals are transmitted to the tire pressure warning antenna and receiver on the body as radio waves and then sent to the tire pressure warning ECU. DTC No. DTC Detection Condition Trouble Area ...

How To Proceed With Troubleshooting
HOW TO PROCEED WITH TROUBLESHOOTING 1. OPERATION FLOW HINT: Perform troubleshooting in accordance with the procedure below. The following is an outline of basic troubleshooting procedure. Confirm the troubleshooting procedure for the circuit you are wor ...