Toyota Avalon (XX50): Check Bus 4 Line for Short to +B

Toyota Avalon (XX50) 2019-2022 Service & Repair Manual / Power Source, Network / Networking / Can Communication System(for Hv Model) / Check Bus 4 Line for Short to +B

DESCRIPTION

There may be a short circuit between one of the CAN bus lines and +B when there is no resistance between terminal 22 (CA2H) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3, or terminal 7 (CA2L) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3.

Symptom	Trouble Area
There is no resistance between terminal 22 (CA2H) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3, or terminal 7 (CA2L) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3.	Short to +B in CAN main bus line Short to +B in CAN branch line Central gateway ECU (network gateway ECU) Occupant detection ECU Tire pressure warning ECU and receiver Rack and pinion power steering gear assembly Brake booster with master cylinder assembly Steering sensor Airbag ECU assembly ECM Brake actuator assembly Hybrid vehicle control ECU No. 2 CAN junction connector No. 4 CAN junction connector No. 1 junction connector

Symptom

Trouble Area

There is no resistance between terminal 22 (CA2H) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3, or terminal 7 (CA2L) of the central gateway ECU (network gateway ECU) and terminal 16 (BAT) of the DLC3.

Short to +B in CAN main bus line
Short to +B in CAN branch line
Central gateway ECU (network gateway ECU)
Occupant detection ECU
Tire pressure warning ECU and receiver
Rack and pinion power steering gear assembly
Brake booster with master cylinder assembly
Steering sensor
Airbag ECU assembly
ECM
Brake actuator assembly
Hybrid vehicle control ECU
No. 2 CAN junction connector
No. 4 CAN junction connector
No. 1 junction connector

WIRING DIAGRAM

CAUTION / NOTICE / HINT

CAUTION:

When performing the confirmation driving pattern, obey all speed limits and traffic laws.

NOTICE:

Because the order of diagnosis is important to allow correct diagnosis, make sure to begin troubleshooting using How to Proceed with Troubleshooting when CAN communication system related DTCs are output.
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Before measuring the resistance of the CAN bus, turn the power switch off and leave the vehicle for 1 minute or more without operating the key or any switches, or opening or closing the doors. After that, disconnect the cable from the negative (-) auxiliary battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
After turning the power switch off, waiting time may be required before disconnecting the cable from the negative (-) auxiliary battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) auxiliary battery terminal notices before proceeding with work.
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After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.
DTC check procedure: Turn the power switch on (IG) and wait for 1 minute or more. Then operate the suspected malfunctioning system and drive the vehicle at 60 km/h (37 mph) or more for 5 minutes or more.
After the repair, perform the CAN bus check and check that all the ECUs and sensors connected to the CAN communication system are displayed as normal.
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HINT:

Before disconnecting related connectors for inspection, push in on each connector body to check that the connector is not loose or disconnected.
When a connector is disconnected, check that the terminals and connector body are not cracked, deformed or corroded.

PROCEDURE

1.	CHECK FOR SHORT TO +B IN CAN BUS LINE (NO. 1 JUNCTION CONNECTOR)

(a) Disconnect the cable from the negative (-) auxiliary battery terminal.

(b) Disconnect the K67 No. 1 junction connector.

*1	DLC3	-	-
*a	Front view of wire harness connector (to No. 1 Junction Connector)	*b	to Tire Pressure Warning ECU and Receiver
*c	to Occupant Detection ECU	*d	to Central Gateway ECU (Network Gateway ECU)
*e	to No. 2 CAN Junction Connector	-	-

Standard Resistance:

Tester Connection	Condition	Specified Condition	Connected to
K67-8 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher	Tire pressure warning ECU and receiver
K67-19 (CANL) - G45-16 (BAT)		6 kΩ or higher	Tire pressure warning ECU and receiver
K67-9 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher	Occupant detection ECU
K67-20 (CANL) - G45-16 (BAT)		6 kΩ or higher	Occupant detection ECU
K67-10 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher	Central gateway ECU (network gateway ECU)
K67-21 (CANL) - G45-16 (BAT)		6 kΩ or higher	Central gateway ECU (network gateway ECU)
K67-11 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher	No. 2 CAN junction connector
K67-22 (CANL) - G45-16 (BAT)		6 kΩ or higher	No. 2 CAN junction connector

Result	Proceed to
OK	A
NG (Line to central gateway ECU (network gateway ECU))	B
NG (Line to No. 2 CAN junction connector)	C
NG (Line to ECU or sensor)	D

REPLACE NO. 1 JUNCTION CONNECTOR

GO TO STEP 3

GO TO STEP 7

2.	CHECK FOR SHORT TO +B IN CAN BUS LINE (NO. 1 JUNCTION CONNECTOR - CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU))

(a) Disconnect the G52 central gateway ECU (network gateway ECU) connector.

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

DLC3

Front view of wire harness connector

(to No. 1 Junction Connector)

to Central Gateway ECU (Network Gateway ECU)

Standard Resistance:

Tester Connection	Condition	Specified Condition
K67-10 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher
K67-21 (CANL) - G45-16 (BAT)		6 kΩ or higher

REPLACE CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU)

REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NO. 1 JUNCTION CONNECTOR - CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU))

3.	CHECK FOR SHORT TO +B IN CAN BUS LINE (NO. 2 CAN JUNCTION CONNECTOR)

(a) Disconnect the A49 No. 2 CAN junction connector.

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

*1	DLC3	-	-
*a	Front view of wire harness connector (to No. 2 CAN Junction Connector)	*b	to Brake Booster with Master Cylinder Assembly
*c	to No. 1 Junction Connector	*d	to ECM
*e	to Rack and Pinion Power Steering Gear Assembly	*f	to No. 4 CAN Junction Connector
*g	to Brake Actuator Assembly	-	-

Standard Resistance:

Tester Connection	Condition	Specified Condition	Connected to
A49-1 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher	Brake booster with master cylinder assembly
A49-12 (CANL) - G45-16 (BAT)		6 kΩ or higher	Brake booster with master cylinder assembly
A49-2 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher	No. 1 junction connector
A49-13 (CANL) - G45-16 (BAT)		6 kΩ or higher	No. 1 junction connector
A49-3 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher	ECM
A49-14 (CANL) - G45-16 (BAT)		6 kΩ or higher	ECM
A49-4 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher	Rack and pinion power steering gear assembly
A49-15 (CANL) - G45-16 (BAT)		6 kΩ or higher	Rack and pinion power steering gear assembly
A49-5 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher	No. 4 CAN junction connector
A49-16 (CANL) - G45-16 (BAT)		6 kΩ or higher	No. 4 CAN junction connector
A49-6 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher	Brake actuator assembly
A49-17 (CANL) - G45-16 (BAT)		6 kΩ or higher	Brake actuator assembly

Result	Proceed to
OK	A
NG (Line to No. 1 junction connector)	B
NG (Line to No. 4 CAN junction connector)	C
NG (Line to ECU or sensor)	D

REPLACE NO. 2 CAN JUNCTION CONNECTOR

REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NO. 2 CAN JUNCTION CONNECTOR - NO. 1 JUNCTION CONNECTOR)

GO TO STEP 7

4.	CHECK FOR SHORT TO +B IN CAN BUS LINE (NO. 4 CAN JUNCTION CONNECTOR)

(a) Disconnect the G96 No. 4 CAN junction connector.

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

DLC3

Front view of wire harness connector

(to No. 4 CAN Junction Connector)

to Hybrid Vehicle Control ECU

to Airbag ECU Assembly

Standard Resistance:

Tester Connection	Condition	Specified Condition	Connected to
G96-5 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher	Hybrid vehicle control ECU
G96-16 (CANL) - G45-16 (BAT)		6 kΩ or higher	Hybrid vehicle control ECU
G96-6 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher	Airbag ECU assembly
G96-17 (CANL) - G45-16 (BAT)		6 kΩ or higher	Airbag ECU assembly

Result	Proceed to
OK	A
NG (Line to airbag ECU assembly)	B
NG (Line to ECU or sensor)	C

GO TO STEP 6

GO TO STEP 7

5.	CHECK FOR SHORT TO +B IN CAN BUS LINE (NO. 4 CAN JUNCTION CONNECTOR)

(a) Disconnect the G95 No. 4 CAN junction connector.

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

DLC3

Front view of wire harness connector

(to No. 4 CAN Junction Connector)

to No. 2 CAN Junction Connector

to Steering Sensor

Standard Resistance:

Tester Connection	Condition	Specified Condition	Connected to
G95-6 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher	No. 2 CAN junction connector
G95-17 (CANL) - G45-16 (BAT)		6 kΩ or higher	No. 2 CAN junction connector
G95-7 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher	Steering sensor
G95-18 (CANL) - G45-16 (BAT)		6 kΩ or higher	Steering sensor

Result	Proceed to
OK	A
NG (Line to No. 2 CAN junction connector)	B
NG (Line to ECU or sensor)	C

REPLACE NO. 4 CAN JUNCTION CONNECTOR

REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NO. 4 CAN JUNCTION CONNECTOR - NO. 2 CAN JUNCTION CONNECTOR)

GO TO STEP 7

6.	CHECK FOR SHORT TO +B IN CAN BUS LINE (NO. 4 CAN JUNCTION CONNECTOR - AIRBAG ECU ASSEMBLY)

(a) Disconnect the G50 airbag ECU assembly connector.

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

DLC3

Front view of wire harness connector

(to No. 4 CAN Junction Connector)

to Airbag ECU Assembly

Standard Resistance:

Tester Connection	Condition	Specified Condition
G96-6 (CANH) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher
G96-17 (CANL) - G45-16 (BAT)		6 kΩ or higher

REPLACE AIRBAG ECU ASSEMBLY

REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NO. 4 CAN JUNCTION CONNECTOR - AIRBAG ECU ASSEMBLY)

7.	CHECK FOR SHORT TO +B IN CAN BUS LINE (ECU OR SENSOR)

(a) Reconnect all wire harness connectors.

(b) Disconnect the connector that includes terminals CANH and CANL from the ECU or sensor to which the bus line shorted to +B is connected.

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DLC3

Component with harness connected

(Central Gateway ECU (Network Gateway ECU))

Standard Resistance:

Tester Connection	Condition	Specified Condition
G52-22 (CA2H) - G45-16 (BAT)	Cable disconnected from negative (-) auxiliary battery terminal	6 kΩ or higher
G52-7 (CA2L) - G45-16 (BAT)		6 kΩ or higher

HINT:

If the resistance changes to 6 kΩ or higher when the connector is disconnected from the ECU or sensor, there may be a short in the ECU or sensor.
If the resistance does not become normal when the connector is disconnected from the ECU or sensor, check for a short to +B in the wire harness and repair or replace the wire harness or connector if necessary.

REPLACE ECU OR SENSOR

REPAIR OR REPLACE HARNESS OR CONNECTOR

Check Bus 3 Line for Short to +B. Check Bus 3 Line for Short to GND. Check Bus 3 Lines for Short Circuit

Check Bus 4 Line for Short to GND

See More:

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