CAN COMMUNICATION SYSTEM 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) Skid control ECU (brake actuator assembly) Driving support ECU assembly (w/ Lexus Safety System +) Front steering control ECU Power steering ECU assembly Absorber control ECU Rear steering control ECU No. 8 CAN junction connector (for RHD) No. 10 CAN junction connector (for LHD) No. 15 CAN junction connector (for LHD) No. 16 CAN junction connector (for RHD) No. 18 CAN junction connector No. 3 CAN junction terminal

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)
Skid control ECU (brake actuator assembly)
Driving support ECU assembly

(w/ Lexus Safety System +)
Front steering control ECU
Power steering ECU assembly
Absorber control ECU
Rear steering control ECU
No. 8 CAN junction connector

(for RHD)
No. 10 CAN junction connector

(for LHD)
No. 15 CAN junction connector

(for LHD)
No. 16 CAN junction connector

(for RHD)
No. 18 CAN junction connector
No. 3 CAN junction terminal

WIRING DIAGRAM

for LHD
*a	Rear Steering Control ECU
*b	No. 18 CAN Junction Connector
*c	No. 3 CAN Junction Terminal

for RHD
*a	Rear Steering Control ECU
*b	No. 18 CAN Junction Connector
*c	No. 3 CAN Junction Terminal

CAUTION / NOTICE / HINT

CAUTION:

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

Note

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.

Click here
Before measuring the resistance of the CAN bus, turn the engine 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 (-) battery terminal and leave the vehicle for 1 minute or more before measuring the resistance.
After turning the engine switch off, waiting time may be required before disconnecting the cable from the negative (-) battery terminal. Therefore, make sure to read the disconnecting the cable from the negative (-) battery terminal notices before proceeding with work.

Click here
After performing repairs, perform the DTC check procedure and confirm that the DTCs are not output again.

DTC check procedure: Turn the engine 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.

Click here

Tech Tips

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

CHECK VEHICLE TYPE

Check vehicle type.

Result

Result	Proceed to
for LHD	A
for RHD	B

CHECK FOR SHORT TO +B IN CAN BUS LINE (NO. 16 CAN JUNCTION CONNECTOR) Click here

CHECK FOR SHORT TO +B IN CAN BUS LINE (NO. 15 CAN JUNCTION CONNECTOR)

Disconnect the cable from the negative (-) battery terminal.
Disconnect the O196 No. 15 CAN junction connector.

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

*1	DLC3	-	-
*a	Front view of wire harness connector (to No. 15 CAN Junction Connector)	*b	to Skid Control ECU (Brake Actuator Assembly)
*c	to Central Gateway ECU (Network Gateway ECU)	*d	to Driving Support ECU Assembly (w/ Lexus Safety System +)
*e	to No. 10 CAN Junction Connector	-	-

Standard Resistance

Tester Connection	Condition	Specified Condition	Connected to
O196-1 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Skid control ECU (brake actuator assembly)
O196-12 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Skid control ECU (brake actuator assembly)
O196-2 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Central gateway ECU (network gateway ECU)
O196-13 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Central gateway ECU (network gateway ECU)
O196-3 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Driving support ECU assembly*
O196-14 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Driving support ECU assembly*
O196-4 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 10 CAN junction connector
O196-15 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 10 CAN junction connector

*: w/ Lexus Safety System +

Result

Result	Proceed to
OK	A
NG (Line to central gateway ECU (network gateway ECU))	B
NG (Line to No. 10 CAN junction connector)	C
NG (Line to ECU or sensor)	D

REPLACE NO. 15 CAN JUNCTION CONNECTOR

CHECK FOR SHORT TO +B IN CAN BUS LINE (NO. 10 CAN JUNCTION CONNECTOR) Click here

GO TO STEP 12 Click here

CHECK FOR SHORT TO +B IN CAN BUS LINE (CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU))

Disconnect the O157 central gateway ECU (network gateway ECU) connector.

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

DLC3

Front view of wire harness connector

(to Central Gateway ECU (Network Gateway ECU))

Standard Resistance

Tester Connection	Condition	Specified Condition
O157-22 (CA2H) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher
O157-7 (CA2L) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher

Result

Result
OK
NG

REPLACE CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU) Click here

REPAIR OR REPLACE CAN BRANCH LINE OR CONNECTOR (CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU) - NO. 15 CAN JUNCTION CONNECTOR)

CHECK FOR SHORT TO +B IN CAN BUS LINE (NO. 10 CAN JUNCTION CONNECTOR)

Disconnect the T32 No. 10 CAN junction connector.

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

*1	DLC3	-	-
*a	Front view of wire harness connector (to No. 10 CAN Junction Connector)	*b	to Front Steering Control ECU
*c	to Power Steering ECU Assembly	*d	to No. 18 CAN Junction Connector
*e	to Absorber Control ECU	*f	to No. 15 CAN Junction Connector

Standard Resistance

Tester Connection	Condition	Specified Condition	Connected to
T32-1 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Front steering control ECU
T32-12 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Front steering control ECU
T32-2 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Power steering ECU assembly
T32-13 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Power steering ECU assembly
T32-3 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 18 CAN junction connector
T32-14 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 18 CAN junction connector
T32-4 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Absorber control ECU
T32-15 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Absorber control ECU
T32-5 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 15 CAN junction connector
T32-16 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 15 CAN junction connector

Result

Result	Proceed to
OK	A
NG (Line to No. 18 CAN junction connector)	B
NG (Line to No. 15 CAN junction connector)	C
NG (Line to ECU or sensor)	D

REPLACE NO. 10 CAN JUNCTION CONNECTOR

REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NO. 10 CAN JUNCTION CONNECTOR - NO. 15 CAN JUNCTION CONNECTOR)

GO TO STEP 12 Click here

CHECK FOR SHORT TO +B IN CAN BUS LINE (NO. 18 CAN JUNCTION CONNECTOR)

Disconnect the U61 No. 18 CAN junction connector.

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

DLC3

Front view of wire harness connector

(to No. 18 CAN Junction Connector)

to No. 10 CAN Junction Connector

to No. 3 CAN Junction Terminal

to Rear Steering Control ECU

Standard Resistance

Tester Connection	Condition	Specified Condition	Connected to
U61-5 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 10 CAN junction connector
U61-16 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 10 CAN junction connector
U61-6 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 3 CAN junction terminal
U61-17 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 3 CAN junction terminal
U61-7 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Rear steering control ECU
U61-18 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Rear steering control ECU

Result

Result	Proceed to
OK	A
NG (Line to No. 3 CAN junction terminal)	B
NG (Line to No. 10 CAN junction connector)	C
NG (Line to ECU or sensor)	D

REPLACE NO. 18 CAN JUNCTION CONNECTOR

REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NO. 18 CAN JUNCTION CONNECTOR - NO. 10 CAN JUNCTION CONNECTOR)

GO TO STEP 12 Click here

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

Disconnect the U55 No. 3 CAN junction terminal connector.

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

DLC3

Front view of wire harness connector

(to No. 3 CAN Junction Terminal)

Standard Resistance

Tester Connection	Condition	Specified Condition
U55-3 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher
U55-2 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher

Result

Result
OK
NG

REPLACE NO. 3 CAN JUNCTION TERMINAL

REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NO. 3 CAN JUNCTION TERMINAL - NO. 18 CAN JUNCTION CONNECTOR)

CHECK FOR SHORT TO +B IN CAN BUS LINE (NO. 16 CAN JUNCTION CONNECTOR)

Disconnect the cable from the negative (-) battery terminal.
Disconnect the T37 No. 16 CAN junction connector.

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

DLC3

Front view of wire harness connector

(to No. 16 CAN Junction Connector)

to Skid Control ECU (Brake Actuator Assembly)

to Absorber Control ECU

to No. 8 CAN Junction Connector

Standard Resistance

Tester Connection	Condition	Specified Condition	Connected to
T37-1 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Skid control ECU (brake actuator assembly)
T37-12 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Skid control ECU (brake actuator assembly)
T37-2 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Absorber control ECU
T37-13 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Absorber control ECU
T37-3 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 8 CAN junction connector
T37-14 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 8 CAN junction connector

Result

Result	Proceed to
OK	A
NG (Line to No. 8 CAN junction connector)	B
NG (Line to ECU or sensor)	C

REPLACE NO. 16 CAN JUNCTION CONNECTOR

GO TO STEP 12 Click here

CHECK FOR SHORT TO +B IN CAN BUS LINE (NO. 8 CAN JUNCTION CONNECTOR)

Disconnect the O110 No. 8 CAN junction connector.

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

*1	DLC3	-	-
*a	Front view of wire harness connector (to No. 8 CAN Junction Connector)	*b	to Front Steering Control ECU
*c	to Power Steering ECU Assembly	*d	to No. 18 CAN Junction Connector
*e	to Central Gateway ECU (Network Gateway ECU)	*f	to Driving Support ECU Assembly (w/ Lexus Safety System +)
*g	to No. 16 CAN Junction Connector	-	-

Standard Resistance

Tester Connection	Condition	Specified Condition	Connected to
O110-1 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Front steering control ECU
O110-12 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Front steering control ECU
O110-2 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Power steering ECU assembly
O110-13 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Power steering ECU assembly
O110-3 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 18 CAN junction connector
O110-14 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 18 CAN junction connector
O110-4 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Central gateway ECU (network gateway ECU)
O110-15 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Central gateway ECU (network gateway ECU)
O110-5 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Driving support ECU assembly*
O110-16 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Driving support ECU assembly*
O110-6 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 16 CAN junction connector
O110-17 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 16 CAN junction connector

*: w/ Lexus Safety System +

Result

Result	Proceed to
OK	A
NG (Line to central gateway ECU (network gateway ECU))	B
NG (Line to No. 18 CAN junction connector)	C
NG (Line to No. 16 CAN junction connector)	D
NG (Line to ECU or sensor)	E

REPLACE NO. 8 CAN JUNCTION CONNECTOR

CHECK FOR SHORT TO +B IN CAN BUS LINE (NO. 18 CAN JUNCTION CONNECTOR) Click here

REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NO. 8 CAN JUNCTION CONNECTOR - NO. 16 CAN JUNCTION CONNECTOR)

GO TO STEP 12 Click here

CHECK FOR SHORT TO +B IN CAN BUS LINE (CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU))

Disconnect the O157 central gateway ECU (network gateway ECU) connector.

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

DLC3

Front view of wire harness connector

(to Central Gateway ECU (Network Gateway ECU))

Standard Resistance

Tester Connection	Condition	Specified Condition
O157-22 (CA2H) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher
O157-7 (CA2L) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher

Result

Result
OK
NG

REPLACE CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU) Click here

REPAIR OR REPLACE CAN BRANCH LINE OR CONNECTOR (CENTRAL GATEWAY ECU (NETWORK GATEWAY ECU) - NO. 8 CAN JUNCTION CONNECTOR)

CHECK FOR SHORT TO +B IN CAN BUS LINE (NO. 18 CAN JUNCTION CONNECTOR)

Disconnect the U61 No. 18 CAN junction connector.

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

DLC3

Front view of wire harness connector

(to No. 18 CAN Junction Connector)

to No. 8 CAN Junction Connector

to No. 3 CAN Junction Terminal

to Rear Steering Control ECU

Standard Resistance

Tester Connection	Condition	Specified Condition	Connected to
U61-5 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 8 CAN junction connector
U61-16 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 8 CAN junction connector
U61-6 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 3 CAN junction terminal
U61-17 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	No. 3 CAN junction terminal
U61-7 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Rear steering control ECU
U61-18 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher	Rear steering control ECU

Result

Result	Proceed to
OK	A
NG (Line to No. 3 CAN junction terminal)	B
NG (Line to No. 8 CAN junction connector)	C
NG (Line to ECU or sensor)	D

REPLACE NO. 18 CAN JUNCTION CONNECTOR

REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NO. 18 CAN JUNCTION CONNECTOR - NO. 8 CAN JUNCTION CONNECTOR)

CHECK FOR SHORT TO +B IN CAN BUS LINE (ECU OR SENSOR) Click here

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

Disconnect the U55 No. 3 CAN junction terminal connector.

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

DLC3

Front view of wire harness connector

(to No. 3 CAN Junction Terminal)

Standard Resistance

Tester Connection	Condition	Specified Condition
U55-3 (CANH) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher
U55-2 (CANL) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher

Result

Result
OK
NG

REPLACE NO. 3 CAN JUNCTION TERMINAL

REPAIR OR REPLACE CAN MAIN BUS LINE OR CONNECTOR (NO. 3 CAN JUNCTION TERMINAL - NO. 18 CAN JUNCTION CONNECTOR)

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

Reconnect all wire harness connectors.
Disconnect the connector that includes terminals CANH and CANL from the ECU or sensor to which the bus line shorted to +B is connected.

Click here

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

DLC3

Component with harness connected

(Central Gateway ECU (Network Gateway ECU))

Standard Resistance

Tester Connection	Condition	Specified Condition
O157-22 (CA2H) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher
O157-7 (CA2L) - O8-16 (BAT)	Cable disconnected from negative (-) battery terminal	6 kΩ or higher

Tech Tips

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.

Result

Result
OK
NG

REPLACE ECU OR SENSOR

REPAIR OR REPLACE HARNESS OR CONNECTOR